History of Dublin to 795
Dublin is Ireland's oldest known settlement. It is also the largest and most populous urban centre in the country, a position it has held continuously since first rising to prominence in the 10th century (with the exception of a brief period in the late 19th and early 20th centuries when it was temporarily eclipsed by Belfast). The historic town grew up on the southern bank of the River Liffey, a few kilometres upstream from the river's outfall into Dublin Bay. The original settlement was situated on a ridge overlooking a shallow ford in  the river, which had probably been a regular crossing-point since earliest times. The bedrock underlying the city is calp limestone, a dark shaly sedimentary rock which was once quarried locally and whose mottled grey appearance can still be seen today in some of the city's oldest buildings. Overlying this is a layer of much looser boulder clay of varying thickness. It is no accident that Dublin became the principal city in Ireland. It is located on the island's only significant coastal plain, which not only forms a natural gateway to the rest of the country but also  looks out towards the country's closest and most influential neighbour, Great Britain. Furthermore, Dublin Bay provided early settlers with a substantial and easily defended harbour, protected to some extent by treacherous sandbanks, shallows and mudflats, and overlooked by the twin sentinels of Howth Head and Killiney Hill. Early history. The first known inhabitants of the Dublin region were hunter-gatherers living during the Later Mesolithic, or Middle Stone Age, around 5500 BC. Shell middens, fish traps and occupation debris, which have been found at a number of locations on and around the shores of Dublin Bay (most notably at  Sutton, on Dalkey Island), at the Diageo site at Victoria Quay and at Spencer Dock, which is situated along the northern quays, near the mouth of the River Liffey, indicate that these early settlers lived off the sea. The first farmers appeared in the Neolithic, or New Stone Age, shortly after 4000 BC. These were the first to erect megalithic monuments and evidence of their culture survives in the burial cairns, passage tombs, portal tombs and wedge tombs that can still be seen in the Dublin Mountains and on the coastal lowlands just to the south of the modern city . Stone axes made of porcellanite from County Antrim or porphyry from Lambay Island have also been discovered at a number of sites in the Dublin region. Pottery too was first manufactured in Ireland during the Neolithic, one of the most noteworthy finds being a funerary bowl which was found in a burial site at Drimnagh, County Dublin. Around 2400 BC metal working made its first appearance in Ireland. Archaeological excavations in Suffolk Street have uncovered prehistoric copper axe-heads – the copper axe being the principal metal artifact during the earliest phase of Irish metallurgy (the so-called Knocknagur Phase, or  Copper Age, which lasted from 2400 to 2200 BC). The Bronze Age, which in Ireland is dated from 2200 to 600 BC, also left its mark on the Dublin region. A variety of bronze and gold artifacts which have been discovered in the vicinity of the modern city – among them cauldrons, side-blown horns, lock rings, sleeve fasteners, striated rings, hair rings and penannular bracelets – indicate a continuous or intermittent settlement of the area. In Ireland the commencement of the Iron Age around 600 BC is generally believed to coincide with the first appearance in this country of Celtic-speaking  peoples. There is little archaeological evidence to support the theory of a large-scale Celtic invasion (or series of invasions), but it is quite possible that small groups of migrants, highly skilled in the art of war and armed with superior iron weaponry, were powerful enough to gain a foothold in the island and eventually succeeded in subjugating or absorbing the pre-Celtic natives; in the 12th century of the Common Era small bands of heavily armed Anglo-Normans did just this, so there is no conceivable reason why it could not also have happened in the pre-Christian era . Iron ores are widely distributed throughout Ireland – one of the country's two richest deposits is to be found in County Wicklow, just a few days' walk from the Dublin region – but there is little archaeological evidence for an urban settlement on the site of the modern city during the Early Iron Age (or Athlone Phase). Excavations at various locations in the region, however, do indicate intermittent occupation at scattered locations throughout this period (e.g. at Taylor's Grange in Rathfarnham, and at Cherrywood near Loughlinstown). Once associated with the Iron Age is the ringfort, or "ráth", a defensive formation  generally consisting of one or more circular earthen embankments surrounded by a ditch. The existence of ringforts in the Dublin region may be deduced from the names of several of the modern city's suburbs: Rathmines, Rathgar, Rathfarnham (on the south side of the city) and Raheny (on the north side). There is also the village of Rathcoole, which lies to the southwest of the modern city. Needless to say the growth of the modern city has all but obliterated these structures, but excavation of ringforts in other parts of the country has sometimes revealed traces of earlier, pre-ringfort  occupation of the same sites. In the Dublin hinterland, surviving ringforts are too numerous to mention individually, though a univallate ringfort at Rathmichael (near Shankill to the southeast of the city) may be noted. The lowlying area to the northwest of the city is particularly rich in ringforts. It is now thought, however, that most of Ireland's ringforts date from the Christian era. Pre-Viking Dublin. Although the site of the modern city of Dublin has been occupied intermittently since the Mesolithic era, it is not known when the first permanent settlement was established. Ptolemy's description of Ireland , which was compiled around 140 AD but which may draw on much earlier accounts, was once thought to contain a reference to Dublin in Eblana, the name of a settlement on the east coast; this, however, is no longer thought likely and the similarity of the two names is probably coincidental. Early Dublin is also referred to in a number of native sources. "The Book of Invasions", a largely fabulous compilation of myths and legends, mentions Dublin when describing how two legendary kings of Ireland, Conn of the Hundred Battles and Mug Nuadat, divided the country between them. The line  of demarcation, which cut the island into two symbolic halves (known as "Leth Cuinn", or "Conn's Half", and "Leth Moga", or "Mug's Half") ran along the Esker Riada from High Street in Dublin to Galway on the west coast. According to another work which draws on early sources, the "Annals of the Four Masters", Fiachu Sraibtine, the king of Tara, quelled the rebellious inhabitants of Leinster in a battle fought at Dublin in 291 AD; the "Annals of Dublin" also record that Alphin mac Eochaid, King of Dublin, was converted to Christianity by Saint Patrick in 448 AD . But these entries were only added to the "Annals"', or the sources from which they were compiled, many centuries after the events they purport to record, and no reliance can be placed on them. The simple fact is that we do not know for certain when the city of Dublin was founded. When contemporary records begin in the 5th century, there is a thriving community of farmers and fishermen in existence in the vicinity of Cornmarket and High Street. A ringed pattern of streets and laneways which can still be discerned in this part of the modern city may be  a relic of the original boundary of an early settlement. Located on a prominent ridge overlooking the River Liffey (previously known as the "Ruirthech", "running swiftly"), this settlement was easily defended and ideally situated to take advantage of the ford, which lay just 100 metres away. The name ford of hurdles – "Áth Cliath" in Irish – suggests that, to facilitate travellers who wished to cross the river dry-shod during low tide, the inhabitants of this settlement constructed a lattice-work of interlaced osiers – "hurdles" – and secured it to the muddy bed of the river, perhaps making use of the fortuitously  placed Usher's Island in the middle of the stream. It is also possible that a series of hurdles used as fish-traps were placed along the banks of the river. The hurdles were probably located about 100 metres west of the point where Father Mathew Bridge now crosses the Liffey, but in the absence of archaeological evidence both its nature and precise location must remain matters of speculation. In ancient times the lower course of the Liffey is believed to have formed part of the boundary between the provinces, or "overkingdoms", of Leinster and Mide (though there is some  conflicting evidence which suggests that the boundary was actually marked by another river, the Tolka, which now discharges into Dublin Bay about a kilometre north of the Liffey). Áth Cliath, which belonged to Leinster, must have been an important trading place thanks to its strategic location on this political boundary. Early roads. It is also hardly a coincidence that four of the five great highways, or of ancient Ireland converged on the site of the medieval city, and not on Tara, as early Irish historians spuriously claimed: These four highways linked Dublin with the five provinces of ancient Ireland: Ulster  and Mide to the north, Connacht to the west, Munster to the southwest and Leinster to the south. Although it is not known when these roads were first constructed, a tract dating from around 700 testifies to their early existence. A fifth, unnamed road may have linked Áth Cliath with Tara, County Meath, the seat of the High Kings of Ireland. It is possible that traces of this road are preserved in the modern thoroughfare that runs northwest from Stoneybatter (i.e. the Stoney "bóthar", or "cow-track") through Ratoath Road in the general direction of Tara. The existence of this  unnamed road suggests that the Slige Midluachra originally by-passed Tara, running north from Dublin to Emain Macha. Áth Cliath was centred on the crossroads formed by the intersection of the Slige Midluachra and Slige Mhór. After the introduction of Christianity a wayside chapel dedicated to St Mo Lua appears to have been erected at this junction, though the earliest reference to such a church is of a much later date. Another early church, dedicated to St Columba, occupied the site of the present Church of St Audoen, which is thought to be the city's oldest surviving church site . The existence of a market place to the east of the junction is suggested by the modern street name of Cornmarket. The southwestern approaches of Áth Cliath may have been protected by a ditch, which is mentioned in two 13th century documents. In addition to the urban settlement at Áth Cliath, the early inhabitants of Dublin may also have constructed a ringfort, or "ráth", on the present site of Dublin Castle. This would have been a relatively easy place to defend, being the highest point in the area and surrounded by water on three sides. It could also explain why  the eastern terminus of the Slige Mhór lay several hundred metres beyond Áth Cliath. If such a rath did exist, it may have been the source of the placename "Druim Cuill-Choille", or "Hazelwood Ridge": according to Harris (1736), this was the city's original name, though no ancient references to such a name are now extant. The name "Baile Átha Cliath" itself was first written down in the Annals of Ulster in 1365, some 200 years after the Norman invasion of Ireland in 1169, and the Irish word "baile" (meaning a town), often anglicized as "bally", derives from Norman -French "bailee" or "ville". It remains unproven that it was called Áth Cliath before 795, but for convenience the western of the two settlements is usually referred to by historians and archaeologists as "Áth Cliath" to distinguish it from "Duiblinn" (see below). The existence of other early ringforts in the vicinity of Áth Cliath may be deduced from the names of several of the modern city's suburbs: Rathmines, Rathgar, Rathfarnham and Raheny, though no firm dates can be assigned to any of these. Duiblinn. By the early 7th century Áth Cliath had acquired a neighbour in the form of  a large and important ecclesiastical settlement about half a kilometre to the southeast. Referred to in various annals and martyrologies as Duiblinn (Modern Irish "Dubhlinn", or "Blackpool"), it took its name from a dark tidal pool in the River Poddle a short distance to the north. (This pool no longer exists, but its location is marked by the site of the Coach House and Castle Gardens at the rear of Dublin Castle.) Covering an area of about 5 hectares, Dubhlinn was one of the largest settlements of its kind in the country, and shared its distinctive pear-shaped outline with  hundreds of other ecclesiastical or quasi-ecclesiastical enclosures of the time. This outline can still be discerned in the morphology of the modern city, especially in the oval configuration of St Peter's Row, Whitefriar Street, Upper and Lower Stephen Street, and Johnson's Place. In later centuries, this area was served by the local parish church of St Peter's on The Mount, which may have replaced a much earlier church. However, recent archaeological excavations at the site of another church, St Michael le Pole, between Chancery Lane and Ship Street, have led some historians to surmise that the  ecclesiastical settlement of Dubhlinn was located here rather than at St Peter's. As its name suggests, St Michael le Pole – that is, "St Michael of the Pool" – overlooked the "Black Pool" from which Dubhlinn took its name. It lay some 300 metres to the west of St Peter's, "outside" the latter's pear-shaped enclosure. In common with many other early sites, St Michael's had a round tower, and it is known to have been in existence by the late seventh century. Graves going back to the 8th century have been unearthed at the site of another  early church, St Bride's (or St Bridget's), on the corner of Bride Road and Bride St. This site may have been part of the same ecclesiastical complex as St Michael le Pole's, though the church of St Bride itself seems to belong to a later period. Whatever its precise location, Dubhlinn probably served as the chief place of worship of the Uí Fergusa, a small and politically insignificant sept of the Uí Dúnlainge (an important confederation of Gaelic septs which monopolised the kingship of Leinster from 738 to 1042). A number of early sources refer to Abbots  and Bishops of Dubhlinn, with little distinction between the two offices. Among these the following may be noted: According to Harris (1736), St Sedulius was the last Abbot of Dublin to be mentioned in the "Annals". In 795, just ten years after his death, the Vikings, or Norsemen, launched their first raid on Irish soil: a new era in the history of Dublin was about to begin.