Keep A keep ( from the Middle English " kype " ) is a type of fortified tower built within castle s during the Middle Ages by European nobility . Scholars have debated the scope of the word " keep " , but usually consider it to refer to large towers in castles that were fortified residences , used as a refuge of last resort should the rest of the castle fall to an adversary . The first keeps were made of timber and formed a key part of the motte and bailey castles that emerged in Normandy and Anjou during the 10th century ; the design spread to England as a result of the Norman invasion of 1066 , and in turn spread into Wales during the second half of the 11th century and into Ireland in the 1170s . The Anglo - Normans and French rulers began to build stone keeps during the 10th and 11th centuries ; these included Norman keeps , with a square or rectangular design , and circular shell keep s . Stone keeps carried considerable political as well as military importance and could take up to a decade to build . During the 12th century new designs began to be introduced – in France , quatrefoil - shaped keeps were introduced , while in England polygon al towers were built . By the end of the century , French and English keep designs began to diverge : Philip II of France built a sequence of circular keeps as part of his bid to stamp his royal authority on his new territories , while in England castles were built that abandoned the use of keeps altogether . In Spain , keeps were increasingly incorporated into both Christian and Islamic castles , although in Germany tall towers called " Bergfried e " were preferred to keeps in the western fashion . In the second half of the 14th century there was a resurgence in the building of keeps . In France , the keep at Vincennes began a fashion for tall , heavily machicolated designs , a trend adopted in Spain most prominently through the Valladolid school of Spanish castle design . Meanwhile , in England tower keeps became popular amongst the most wealthy nobles : these large keeps , each uniquely designed , formed part of the grandest castles built during the period . By the 16th century , however , keeps were slowly falling out of fashion as fortifications and residences . Many were destroyed between the 17th and 18th centuries in civil wars , or incorporated into gardens as an alternative to follies . During the 19th century , keeps became fashionable once again and in England and France a number were restored or redesigned by Gothic architects . Despite further damage to many French and Spanish keeps during the wars of the 20th century , keeps now form an important part of the tourist and heritage industry in Europe . Etymology and historiography . Since the 16th century , the English word " keep " has commonly referred to large towers in castles . The word originates from around 1375 to 1376 , coming from the Middle English term " kype " , meaning basket or cask , and was a term applied to the shell keep at Guînes , said to resemble a barrel . The term came to be used for other shell keeps by the 15th century . By the 17th century , the word keep lost its original reference to baskets or casks , and was popularly assumed to have come from the Middle English word " keep " , meaning to hold or to protect . Early on , the use of the word " keep " became associated with the idea of a tower in a castle that would serve both as a fortified , high - status private residence and a refuge of last resort . The issue was complicated by the building of fortified Renaissance towers in Italy called " tenazza " that were used as defences of last resort and were also named after the Italian for " to hold " or " to keep " . By the 19th century Victorian historians incorrectly concluded that the etymology of the words " keep " and " tenazza " were linked , and that all keeps had fulfilled this military function . As a result of this evolution in meaning , the use of the term " keep " in historical analysis today can be problematic . Contemporary medieval writers used various terms for the buildings we would today call keeps . In Latin , they are variously described as " turris " , " turris castri " or " magna turris " – a " tower " , a " castle tower " , or a " great tower " . The 12th - century French came to term them a " " , a corruption of the Latin " dominarium " or " lordship " , linking the keep and feudal authority . Similarly , medieval Spanish writers called the buildings " " , or " place of homage . " In England , " donjon " was later corrupted to " dungeon " , which initially referred to a keep , rather than to a place of imprisonment . This ambiguity over terminology has made historical analysis of the use of " keeps " problematic . While the term remains in common academic use , some academics prefer to use the term " donjon " , and most modern historians warn against using the term " keep " simplistically . The fortifications that we would today call keeps certainly did not necessarily form part of a unified medieval style , nor were they all used in a similar fashion during the period . History . Timber keeps ( 9th – 12th centuries ) . The earliest keeps were built as part of motte - and - bailey castles from the 10th century onwards – a combination of documentary and archaeological evidence places the first such castle , built at Vincy , in 979 . These castles were initially built by the more powerful lords of Anjou in the late 10th and 11th centuries , in particular Fulk III and his son , Geoffrey II , who built a great number of them between 987 and 1060 . William the Conqueror then introduced this form of castle into England when he invaded in 1066 , and the design spread through south Wales as the Normans expanded up the valleys during the subsequent decades . In a motte and bailey design , a castle would include a mound called a motte , usually artificially constructed by piling up turf and soil , and a bailey , a lower walled enclosure . A keep and a protective wall would usually be built on top of the motte . Some protective walls around a keep would be large enough to have a wall - walk around them , and the outer walls of the motte and the wall - walk could be strengthened by filling in the gap between the wooden walls with earth and stones , allowing it to carry more weight – this was called a " garillum " . Smaller mottes could only support simple towers with room for a few soldiers , whilst larger mottes could be equipped with a much grander keep . Many wooden keeps were designed with a " bretasche " , a square structure that overhung from the upper floors of the building , enabling better defences and a more sturdy structural design . These wooden keeps could be protected by skins and hides to prevent them being easily set alight during a siege . One contemporary account of these keeps comes from Jean de Colmieu around 1130 , who described how the nobles of the Calais region would build " a mound of earth as high as they can and dig a ditch about it as wide and deep as possible . The space on top of the mound is enclosed by a palisade of very strong hewn logs , strengthened at intervals by as many towers as their means can provide . Inside the enclosure is a citadel , or keep , which commands the whole circuit of the defences . The entrance to the fortress is by means of a bridge , which , rising from the outer side of the moat and supported on posts as it ascends , reches to the top of the mound . " At Durham Castle , contemporaries described how the keep arose from the " tumulus of rising earth " with a keep reaching " into thin air , strong within and without " , a " stalwart house . . . glittering with beauty in every part " . As well as having defensive value , keeps and mottes sent a powerful political message to the local population . Wooden keeps could be quite extensive in size , and as Robert Higham and Philip Barker have noted , it was possible to build " . . . very tall and massive structures . " As an example of what these keeps may have comprised , the early 12th - century chronicler Lambert of Ardres described the wooden keep on top of the motte at the castle of Ardres , where the " . . . first storey was on the surface of the ground , where were cellars and granaries , and great boxes , tuns , casks , and other domestic utensils . In the storey above were the dwelling and common living - rooms of the residents in which were the larders , the rooms of the bakers and butlers , and the great chamber in which the lord and his wife slept . . . In the upper storey of the house were garret rooms . . . In this storey also the watchmen and the servants appointed to keep the house took their sleep . " In the Holy Roman Empire tall , free - standing wooden towers called " Bergfried e " were commonly built by the 11th century , either as part of motte - and - bailey designs , or as part of " Hohenburgen " castles , with characteristic inner and outer courts . " Bergfriede " , which take their name from the German for a belfry , had similarities to keeps , but are usually distinguished from them on account of " Bergfriede " having a smaller area or footprint , usually being non - residential and being typically integrated into the outer defences of a castle , rather than being a safe refuge of last resort . Early stone keeps ( 10th – 12th centuries ) . During the 10th century a small number of stone keeps began to be built in France , such at the Château de Langeais : in the 11th century their numbers increased as the style spread through Normandy across the rest of France and into England . Some existing motte and bailey castles were converted to stone , with the keep amongst usually the first parts to be upgraded , while in other cases new keeps were built from scratch in stone . These stone keeps were introduced into Ireland during the 1170s following the Norman occupation of the east of the country , where they were particularly popular amongst the new Anglo - Norman lords . Two broad types of design emerged across France and England during the period : four - sided stone keeps , known as Norman keeps or great keeps in English – a " donjon carré " or " donjon roman " in French – and circular shell keep s . The reasons for the transition from timber to stone keeps is unclear , and the process was slow and uneven , taking many years to take effect across the various regions . Traditionally it was believed that stone keeps had been adopted because of the cruder nature of wooden buildings , the limited lifespan of wooden fortifications and their vulnerability to fire ; recent archaeological studies have however shown that many wooden castles were as robust and as sophisticated as their stone equivalents . Some wooden keeps were not converted into stone for many years and were instead expanded in wood , such as at Hen Domen . Nonetheless , stone became increasingly popular as a building material for keeps for both military and symbolic reasons . Stone keep construction required skilled craftsmen . Unlike timber and earthworks , which could be built using unfree labour or serfs , these craftsmen had to be paid and stone keeps were therefore expensive . They were also relatively slow to erect , due to the limitations of the lime mortar used during the period – a keep ' s walls could usually only be raised by a maximum of 12 feet ( 3 . 6 metres ) a year , the keep at Scarborough was not atypical in taking ten years to build . The number of such keeps remained relatively low : in England , for example , although several early stone keeps had been built after the conquest , there were only somewhere between ten and fifteen in existence by 1100 , and only around a hundred had been built by 1216 . Norman keeps had four sides , with the corners reinforced by pilaster buttress es ; some keeps , particularly in Normandy and France , had a " barlongue " design , being rectangular in plan with their length twice their width , while others , particularly in England , formed a square . These keeps could be up to four storeys high , with the entrance placed on the first storey to prevent the door from being easily broken down ; early French keeps had external stairs in wood , whilst later castles in both France and England built them in stone . In some cases the entrance stairs were protected by additional walls and a door , producing a forebuilding . The strength of the Norman design typically came from the thickness of the keep ' s walls : usually made of rag - stone , these could be up to 24 feet ( 7 . 3 metres ) thick , immensely strong and producing a steady temperature inside the building throughout summer and winter . The larger keeps were subdivided by an internal wall while the smaller versions had a single , slightly cramped chamber on each floor . Usually only the first floor would be vaulted in stone , with the higher storeys supported with timbers . There has been extensive academic discussion of the extent to which Norman keeps were designed with a military or political function in mind , particularly in England . Earlier analyses of Norman keeps focused on their military design , and historians such as R . Brown Cathcart King proposed that square keeps were adopted because of their military superiority over timber keeps . Most of these Norman keeps were certainly extremely physically robust , even though the characteristic pilaster buttresses added little real architectural strength to the design . Many of the weaknesses inherent to their design were irrelevant during the early part of their history . The corners of square keeps were theoretically vulnerable to siege engines and galleried mining , but before the introduction of the trebuchet at the end of the 12th century , early artillery stood little practical chance of damaging the keeps , and galleried mining was rarely practised . Similarly , the corners of a square keep created dead space that defenders could not fire at , but missile fire in castle sieges was less important until the introduction of the crossbow in the middle of the 12th century , when arrowslit s began to be introduced . Nonetheless , many stone Norman keeps made considerable compromises to military utility . Norwich Castle , for example , included elaborate blind arcading on the outside of the building and appears to had an entrance route designed for public ceremony , rather than for defence . The interior of the keep at Hedingham could certainly have hosted impressive ceremonies and events , but contained numerous flaws from a military perspective . Important early English and Welsh keeps such as the White Tower , Colchester and Chepstow were all built in a distinctive Romanesque style , often reusing Roman materials and sites , and were almost certainly intended to impress and generate a political effect amongst local people . The political value of these keep designs , and the social prestige they lent to their builders , may help explain why they continued to be built in England into the late 12th century , beyond the point when military theory would have suggested that alternative designs were adopted . The second early stone design , emerging from the 12th century onwards , was the shell keep , a " donjon annulaire " in French , which involved replacing the wooden keep on a motte , or the palisade on a ringwork , with a circular stone wall . Shell keeps were sometimes further protected by an additional low protective wall , called a chemise , around their base . Buildings could then be built around the inside of the shell , producing a small inner courtyard at the centre . The style was particularly popular in south - east England and across Normandy , although less so elsewhere . Restormel Castle is a classic example of this development , as is the later Launceston Castle ; prominent Normandy and Low Country equivalents include Gisors and the Burcht van Leiden – these castles were amongst the most powerful fortifications of the period . Although the circular design held military advantages over one with square corners , as noted above these only really mattered from the end of the 12th century onwards ; the major reason for adopting a shell keep design , in the 12th century at least , was the circular design of the original earthworks exploited to support the keep ; indeed , some designs were less than circular in order to accommodate irregular mottes , such as that found at Windsor Castle . Mid - medieval keeps ( late 12th – 14th centuries ) . During the second half of the 12th century a range of new keep designs began to appear across France and England , breaking the previous unity of the regional designs ; the use of keeps in castles spread through Iberia , while some new castles removed keeps from their designs altogether . One traditional explanation for these developments emphasises the military utility of the new approaches , arguing , for example , that the curved surfaces of the new keeps helped to deflect attacks , or that they drew on lessons learnt during the Crusades from Islamic practices in the Levant . More recent historical analysis , however , has emphasised the political and social drivers that underlay these mid - medieval changes in keep design . Through most of the 12th century , France was divided between the Capetian kings , ruling from the Île - de - France , and kings of England , who controlled Normandy and much of the west of France . Within the Capetian territories , early experimentation in new keep designs began at Houdan in 1120 , where a circular keep was built with four round turrets ; internally , however , the structure remained conventionally square . A few years later , Château d ' Étampes adopted a quatrefoil design . These designs , however , remained isolated experiments . In the 1190s , however , the struggle for power in France began to swing in favour of Philip II , culminating in the Capetian capture of Normandy in 1204 . Philip II started to construct completely circular keeps , such as the Tour Jeanne d ' Arc , with most built in his newly acquired territories . The first of Philip ' s new keeps was begun at the Louvre in 1190 and at least another twenty followed , all built to a consistent standard and cost . The architectural idea of circular keeps may have come from Catalonia , where circular towers in castles formed a local tradition , and probably carried some military advantages , but Philip ' s intention in building these new keeps in a fresh style was clearly political , an attempt to demonstrate his new power and authority over his extended territories . As historian Philippe Durand suggests , these keeps provided military security and were a physical representation of the " renouveau capétian " , or Capetian renewal . Keep design in England only began to change towards the end of the 12th century , later than in France . Wooden keeps on mottes ceased to be built across most of England by the 1150s , although they continued to be erected in Wales and along the Welsh Marches . By the end of the 12th century , England and Ireland saw a handful of innovative angular or polygonal keeps built , including the keep at Orford Castle , with three rectangular , clasping towers built out from the high , circular central tower ; the cross - shaped keep of Trim Castle and the famous polygonal design at Conisborough . Despite these new designs , square keeps remained popular across much of England , and as late as the 1170s square Norman great keeps were being built at Newcastle . Circular keep designs similar to those in France only really became popular in Britain in the Welsh Marches and Scotland for a short period during the early 13th century . As with the new keeps constructed in France , these Anglo - Norman designs were informed both by military thinking and by political drivers . The keep at Orford has been particularly extensively analysed in this regard , and although traditional explanations suggested that its unusual plan was the result of an experimental military design , more recent analysis concludes that the design was instead probably driven by political symbolism and the need for Henry to dominate the contested lands of East Anglia . The architecture would , for mid - 12th century nobility , have summoned up images of King Arthur or Constantinople , then the idealised versions of royal and imperial power . Even formidable military designs such as that at Château Gaillard were built with political effect in mind . Gaillard was designed to reaffirm Angevin authority in a fiercely disputed conflict zone and the keep , although militarily impressive , contained only an anteroom and a royal audience chamber , and was built on soft chalk and without an internal well , both serious defects from a defensive perspective . During most of the medieval period , Iberia was divided between Christian and Islamic kingdoms , neither of which traditionally built keeps , instead building watchtowers or mural towers . By the 12th century , however , the influence of France and the various military order s was encouraging the development of square keeps in Christian castles across the region , and by the second half of the century this practice was spread across into the Islamic kingdoms . By contrast , the remainder of Europe saw stone towers being used in castles , but not in a way that fulfilled the range of functions seen in the western European keeps . In the Low Countries , it became popular for the local nobility to build stand - alone , square towers , but rarely as part of a wider castle . Similarly , square stone towers became popular in Venice , but these did not fulfil the same role as western keeps . In Germany , rectangular stone castles began to replace motte and bailey castles from the 12th century onwards . These designs included stone versions of the traditional Bergfriede , which still remained distinct from the domestic keeps used in more western parts of Europe , with the occasional notable exception , such as the large , residential " Bergfried " at Eltville Castle . Several approaches to designing new castles emerged that totally removed the requirement for keeps . One such design was the concentric approach , involving exterior walls guarded with towers , and perhaps supported by further , concentric layered defenses : thus castles such as Framlingham often dispensed with a central keep altogther . Military factors may well have driven this development : R . Brown , for example , suggests that designs with a separate keep and bailey system inherently lacked a co - ordinated and combined defensive system , and that once bailey walls were sophisticated enough , a keep became militarily unnecessary . In England , gatehouse s were also growing in size and sophistication until they too challenged the need for a keep in the same castle . The classic Edwardian gatehouse , with two large , flanking towers and multiple portcullises , designed to be defended from attacks both within and outside the main castle , has been often compared to the earlier Norman keeps : some of the largest gatehouses are called gatehouse keeps for this reason . The quadrangular castle design that emerged in France during the 13th century was another development that removed the need for a keep . Castles had needed additional living space since their first emergence in the 9th century ; initially this had been provided by halls in the bailey , then later by ranges of chambers alongside the inside of a bailey wall , such as at Goodrich . But French designs in the late 12th century took the layout of a contemporary unfortified manor house , whose rooms faced around a central , rectangular courtyard , and built a wall around them to form a castle . The result , illustrated initially at Yonne , and later at Château de Farcheville , was a characteristic quadrangular layout with four large , circular corner towers . It lacked a keep , which was not needed to support this design . Late medieval keeps ( 14th – 16th centuries ) . The end of the medieval period saw a fresh resurgence in the building of keeps in western castles . Some castles continued to be built without keeps : the Bastille in the 1370s , for example , combined a now traditional quadrangular design with machicolated corner towers , gatehouses and moat , the walls , innovatively , were of equal height to the towers . This fashion became copied across French and in England , particularly amongst the " nouveau riche " , for example at Nunney . The royalty and the very wealthiest in France , England and Spain , however , began to construct a small number of keeps on a much larger scale than before , in England sometimes termed tower keeps , as part of new palace fortresses . This shift reflected political and social pressures , such as the desire of the wealthiest lords to have privacy from their growing households of retainers , as well as the various architectural ideas being exchanged across the region , despite the ongoing Hundred Years War between France and England . The resurgence in French keep design began after the defeat of the royal armies at the battles of Crécy in 1346 and Poitiers in 1356 , which caused high levels of social unrest across the remaining French territories . Charles V of France attempted to restore French royal authority and prestige through the construction of a new range of castles . The Château de Vincennes , where a new keep was completed under Charles by 1380 , was the first example of these " palace fortresses " . The keep at Vincennes was highly innovative : six stories high , with a " chemin de ronde " running around the machicolated battlements , the luxuriously appointed building was protected by an " enceinte " wall that formed a " fortified envelope " around the keep . The Vincennes keep was copied elsewhere across France , particularly as the French kings reconquered territories from the English , encouraging a style that emphasised very tall keeps with prominent machicolations . No allowance for the emerging new gunpowder weapons was made in these keeps , although later in the century gunport s were slowly being added , as for example by Charles VI to his keep at Saint - Malo . The French model spread into Iberia in the second half of the century , where the most powerful nobles in Castile built a number of similar tall keeps , such as that at Peñafiel , taking advantage of the weakness of the Castilian Crown during the period . Henry IV of Castile responded in the 15th century by creating a sequence of royal castles with prominent keeps at the Castle of La Mota , Portillo and Alcázar of Segovia : built to particular proportions , these keeps became known as a key element of the Valladolid school of Spanish castle design . Smaller versions of these keeps were subsequently built by many aspiring new aristocracy in Spain , including many converted Jews , keen to improve their social prestige and position in society . The French model of tall keeps was also echoed in some German castles , such as that at Karlštejn , although the layout and positioning of these towers still followed the existing " bergfried " model , rather than that in western castles . The 15th and 16th centuries saw a small number of English and occasional Welsh castles develop still grander keeps . The first of these large " tower keeps " were built in the north of England during the 14th century , at locations such as Warkworth . They were probably partially inspired by designs in France , but they also reflected the improvements in the security along the Scottish border during the period , and the regional rise of major noble families such as the Percies and the Nevilles , whose wealth encouraged a surge in castle building at the end of the 14th century . New castles at Raby , Bolton and Warkworth Castle took the quadrangular castle styles of the south and combined them with exceptionally large tower keeps to form a distinctive , northern style . Built by major noble houses , these castles were typically even more opulent than the smaller castles like Nunney , built by the " nouveau riche " . They marked what historian Anthony Emery has described as a " . . . second peak of castle building in England and Wales , " following on from the Edwardian designs at the end of the 14th century . In the 15th century the fashion for the creation of very expensive , French - influenced palatial castles featuring complex tower keeps spread , with new keeps being built at Wardour , Tattershall and Raglan Castle . In central and eastern England some keeps began to be built in brick , with Caister and Tattershall forming examples of this trend . In Scotland , the construction of Holyrood Great Tower between 1528 and 1532 drew on this English tradition , but incorporated additional French influences to produce a highly secure but comfortable keep , guarded by a gun park . These tower keeps were expensive buildings to construct , each built to a unique design for a specific lord and , as historian Norman Pounds has suggested , they " . . . were designed to allow very rich men to live in luxury and splendour . " At the same time as these keeps were being built by the extremely wealthy , much smaller , keep - like structures called tower house s or peel tower s were built across Ireland , Scotland and northern England , often by relatively poorer local lords and landowners . It was originally argued that Irish tower houses were based on the Scottish design , but the pattern of development of such castles in Ireland does not support this hypothesis . A tower house would typically be a tall , square , stone - built , crenelated building ; Scottish and Ulster tower houses were often also surrounded by a barmkyn or bawn wall . Most academics have concluded that tower houses should not be classified as keeps but rather as a form of fortified house . As the 16th century progressed , keeps fell out of fashion once again . In England , the gatehouse also began to supplant the keep as the key focus for a new castle development . By the 15th century it was increasingly unusual for a lord to build both a keep and a large gatehouse at the same castle , and by the early 16th century the gatehouse had easily overtaken the keep as the more fashionable feature : indeed , almost no new keeps were built in England after this period . The classical Palladian style began to dominate European architecture during the 17th century , causing a further move away from the use of keeps . Buildings in this style usually required considerable space for the enfiladed formal rooms that became essential for modern palaces by the middle of the century , and this style was impossible to fit into a traditional keep . The keep at Bolsover Castle in England was one of the few to be built as part of a Palladian design . Later use and destruction of keeps ( 17th – 21st centuries ) . From the 17th century onwards , some keeps were deliberately destroyed . In England , many were destroyed after the end of the Second English Civil War in 1649 , when Parliament took steps to prevent another royalist uprising by slighting , or damaging , castles so as to prevent them from having any further military utility . Slighting was quite expensive and took considerable effort to carry out , so damage was usually done in the most cost efficient fashion with only selected walls being destroyed . Keeps were singled out for particular attention in this process because of their continuing political and cultural importance , and the prestige they lent their former royalist owners – at Kenilworth , for example , only the keep was slighted , and at Raglan the keep was the main focus of parliamentary activity . There were some equivalent destruction of keeps in France in the 17th and 18th centuries , such as the slighting of Montaiguillon by Cardinal Richelieu in 1624 , but the catalogue of damage was far less than that of the 1640s and early 1650s in England . In England , ruined medieval castles became fashionable again in the middle of the 18th century . They were considered an interesting counterpoint to Palladian classical architecture , and gave a degree of medieval allure to their owners . Some keeps were modified to exaggerate this effect : Hawarden , for example , was remodelled to appear taller but also more decayed , the better to produce a good silhouette . The interest continued , and in the late 18th and 19th century it became fashionable to build intact , replica castles in England , resulting in what A . Rowan has called the " Norman style " of new castle building , characterised by the inclusion of large keeps ; the final replica keep to be built in this way was at Penrhyn between 1820 and 1840 . Where there was an existing castle on a site , another response across 19th - century Europe was to attempt to improve the buildings , bringing their often chaotic historic features into line with a more integrated architectural aesthetic , in a style often termed Gothic Revivalism . There were numerous attempts to restore or rebuild keeps so as to produce this consistently Gothic style : in England , the architect Anthony Salvin was particularly prominent – as illustrated by reworking and heightening of the keep at Windsor Castle , while in France , Eugène Viollet - le - Duc reworked the keeps at castles in locations like Pierrefonds during the 1860s and 1870s , admittedly in a largely speculative fashion , since the original keep had been mostly destroyed in 1617 . The Spanish Civil War and First and Second World War s in the 20th century caused damage to many castle keeps across Europe ; in particular , the famous keep at Coucy was destroyed by the German Army in 1917 . By the late 20th century , however , the conservation of castle keeps formed part of government policy across France , England , Ireland and Spain . In the 21st century in England , most keeps are ruined and form part of the tourism and heritage industries , rather than being used as functioning buildings – the keep of Windsor Castle being a rare exception . This is contrast to the fate of " bergfried " towers in Germany , large numbers of which were restored as functional buildings in the late 19th and early 20th century , often as government offices or youth hostel s , or the modern conversion of tower houses , which in many cases have become modernised domestic homes .