1994:061 - DUBLIN: Dublin Castle, Dublin

The site lay within the grounds of Dublin Castle, to the south of the Clock Tower building. It formed part of an area known, in the medieval sources, as 'the poll' and was thought to form part of the 'Black Pool' from which Dublin (Dubh linn) took its name. In advance of construction work on the Clock Tower building, it was decided to excavate a long trench in an attempt to identify the location of the pool. The excavation took place between June 13–30, 1994, on behalf of the Office of Public Works.

The Pool
The pool was formed by the action of the Poddle river, approaching from the south, meeting with the tidal waters of the Liffey. Previous excavations at Dublin Castle have revealed Viking fortifications on the northern bank of the pool, on a high ridge. The Anglo-Norman castle, which was constructed in the early 13th century, replaced the earlier Viking fortification.

The 'Poll' area was well-developed prior to the Anglo-Norman arrival at Dublin. To the west of the site lay the early church site of St Michael le Pole with its associated round tower and graveyard. In addition, documentary sources indicate that this area was held by the Mac Torcaill family, rulers in Dublin until the Anglo-Norman invasion in 1170. After the invasion the Poddle was re-channeled in an artificial watercourse and the area was settled. Excavations at Ship St. located structures dating from the 13th century onwards.

In the mid-18th century the area was developed as a military barracks, part of which still occupies the site.

The Excavation
The trench measured 17.5m east-west by 5m north-south and was 7m deep. Bedrock was encountered at 2.96m O.D. and it was evident that all the overlying layers were re-deposited in the post-medieval period. As a result no medieval archaeological deposits were located in situ although one deposit did produce a medieval sherd of Dublin Cooking Ware.

The Quarry
The bedrock exposed represents an extensive quarry pit. One large deposit, approx. 0.5m in depth, comprised small fragments of chipped limestone interpreted as quarry waste. Several other deposits also had a high concentration of chippings. When the quarry went out of use the area was then backfilled with a series of clays interleaved with layers of domestic refuse. The clays varied in colour and type and, while none were water-deposited, some showed evidence of water action in the form of lenses of sand, silt and pebbles. There were two main phases of deposition. However, the pottery finds indicate a similar date for both phases, some time in the late 17th/early 18th century.

The quarrying effectively removed any medieval deposits which may have survived at the site.

Post-medieval Buildings
Several solid post-medieval walls were located during clearance of the site, constructed of large limestone blocks measuring, on average, 0.2m by 0.6m. These were identified as representing the foundations of the Royal Exchequer's Office depicted on the Ordnance Survey of 1837.

45 Wyattville Place, Loughlinstown, Co. Dublin