Folly

In architecture, a folly is a building usually constructed strictly for aesthetic pleasure. Originally, buildings were made to provide shelter or to house people. Follies are just decoration; they no longer have a building's original function.
They were first constructed to put accents into parks and estates. "Folly" is used in the sense of fun or light-heartedness, not in the sense of something ill-advised.
Characteristics
In general, follies have the following properties:
They are buildings, or parts of buildings. This makes them clearly different from other garden ornaments such as sculpture.
They have no purpose other than as an ornament. Often they have some of the appearance of a building constructed for a particular purpose, but this appearance is a sham.
They are purpose-built. Follies are deliberately built as ornaments.
They are often eccentric in design or construction. This is not strictly necessary; however, it is common for these structures to call attention to themselves through unusual details or form.
There is often an element of fakery in their construction. Perhaps the best example of this is the make-believe ruin: a folly which pretends to be the remains of an old building but which was in fact constructed in that state.
In England, these structures are also called "eye-catchers". This points to their basically decorative nature.
Related types
Follies fall within the general realm of fanciful and impractical architecture, and whether a particular structure is a folly is sometimes a matter of opinion. However, there are several types which are related but which can be distinguished from follies.
Fantasy and novelty buildings are essentially the converse of follies. Follies often look like real, usable buildings, but never are; novelty buildings are usable, but have fantastic shapes. The many American shops and water towers in the shapes of commonplace items, for example, are not properly follies.
Eccentric structures may resemble follies, but the mere presence of eccentricity is not proof that a building is a folly. Many mansions and castles are quite eccentric, but being purpose-built to be used as residences, they are not properly follies.
Some structures are popularly referred to as "follies" because they failed to fulfill their intended use. Their design and construction may be foolish, but in the architectural sense, they are not follies.
Visionary art structures frequently blur the line between artwork and folly, if only because it is rather often hard to tell what intent the artist had. The word "folly" carries the connotation that there is something frivolous about the builder's intent, and it is hard to say whether a structure like the Watts Towers was constructed "seriously". Some works (such as the massive complex by Ferdinand Cheval) are considered as follies because they are in the form of useful buildings, but are plainly constructions of extreme and intentional impracticality.
Amusement parks, fairgrounds, and expositions often have fantastical buildings and structures. Some of these are follies, and some are not; the distinction, again, comes in their usage. Shops, restaurants, and other amusements are often housed in strikingly odd and eccentric structures, but these are not follies. On the other hand, fake structures which serve no other purpose than decoration are also common, and these are follies.
History
Follies began as decorative accents on the great estates of the late 16th and early 17th centuries but they flourished especially in the two centuries which followed. Many estates were blessed with picturesque ruins of monastic houses and (in Italy) Roman villas; others, lacking such buildings, constructed their own sham versions of these romantic structures. Such structures were often dubbed "[name of architect or builder]'s Folly", after the single individual who commissioned or designed the project. However, very few follies are completely without a practical purpose. Apart from their decorative aspect, many originally had a use which was lost later, such as hunting towers. Follies are misunderstood structures, according to The Folly Fellowship, a charity that exists to celebrate the history and splendour of these often neglected buildings.
Follies are often found in parks or large grounds of houses and stately homes. Some were deliberately built to look partially ruined. They were especially popular from the end of the 16th century to the 18th century. Theme parks and world's fairs have often contained "follies", although such structures do serve a purpose of attracting people to those parks and fairs.
Famine Follies
The Irish Potato Famine of 1845-49 led to the building of several follies. The society of the day held that laissez faire, not a welfare state, was the appropriate form of civil management. The concept of a welfare state was a century away, and at that time reward without labour, even to those in need, was seen as misguided. However, to hire the needy for work on useful projects would deprive existing workers of their jobs. Thus, construction projects termed "famine follies" came to be built. These include: roads in the middle of nowhere, between two seemingly random points; screen and estate walls; piers in the middle of bogs; etc.
Examples
Follies can be found worldwide, but there seem to be many in Great Britain.
France
Desert de Retz, folly garden in Chambourcy near Paris, France (18th century)
Parc de la Villette in Paris has a number of modern follies by architect Bernard Tschumi.
Ferdinand Cheval in Chateauneuf-de-Galaure, built what he called an Ideal Palace, seen as an example of naive architecture.
Malaysia
Kellie's Castle, Perak
Hungary
Bory Castle at Szekesfehervar
Tarodi Castle at Sopron
Vajdahunyad vara in the City Park of Budapest
India
Overbury's Folly, Thalassery, Kerala
Ireland
Casino at Marino
Conolly's Folly
Italy
The Bomarzo Gardens
Romania
Iulia Hasdeu Castle
Russia
Ruined towers in Peterhof, Tsarskoe Selo, Gatchina, and Tsaritsino
Creaking Pagoda and Chinese Village in Tsarskoe Selo
Dutch Admiralty in Tsarskoe Selo
Ukraine
Swallow's Nest near Yalta
United Kingdom
Ashton Memorial, Lancaster, England
Beckford's Tower, Somerset, England
Broadway Tower, The Cotswolds, England
Bettisons Folly, Hornsea, England
Black Castle Public House, Bristol, England
The Cage at Lyme Park, Cheshire, England
The Castle at Roundhay Park, Leeds, England
Clavell Tower, Dorset, England
Clytha Castle Monmouthshire
The Caldwell Tower, Lugton, Renfrewshire, Scotland.
Dunmore Pineapple, Falkirk, Scotland
Faringdon Folly, Faringdon, Oxfordshire
Flounder's Folly, Shropshire, England
The Folly Tower at Pontypool, Wales
Fonthill Abbey, Wiltshire, England
Fort Belvedere, Surrey, England
Freston Tower, near Ipswich, Suffolk
Gothic Tower at Goldney Hall, Bristol
The Great Pagoda at the Royal Botanic Gardens, Kew, London"
Gwrych Castle, one of Europe's largest follies, Abergele, North Wales
Hawkstone Park, follies and gardens in Shropshire, England
Hume Castle. Berwickshire, Scotland
King Alfred's Tower, Stourhead, Wiltshire, England
McCaig's Tower, Oban, Scotland
Mow Cop Castle, Cheshire, England
National Monument, Edinburgh, Scotland
Old John, Bradgate Park, Leicestershire, England
Penshaw Monument, Penshaw, Sunderland, England
Perrott's Folly, Birmingham, England
Pope's Grotto, Twickenham, south west London, England.
Portmeirion, Wales
Rushton Triangular Lodge, Northamptonshire (16th century)
Severndroog Castle, Shooter's Hill, south-east London
Stowe School has several follies in the grounds
Sway Tower, New Forest, England
Tattingstone Wonder, near Ipswich, Suffolk
The Temple near Castle Semple Loch, Renfrewshire, Scotland.
Wentworth Follies, Wentworth, South Yorkshire
Williamson's tunnels, probably the largest underground folly in the world, Liverpool, England
United States
Belvedere Castle, New York City
Lawson Tower, Scituate, Massachusetts
Lucy the Elephant, Margate City, New Jersey
Bishop Castle, outside of Pueblo, Colorado
Korner's Folly, Kernersville, North Carolina
Other websites
The Folly Fellowship- An organization which celebrates architectural follies
Follies in the English Landscape
Follies and Monuments - A comprehensive catalogue of Follies within the UK
Images of follies on Odd-stuff!