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Dublin
Dalkey Island, Co. Dublin
Early Medieval Promontory Fort
Grid reference: O27702645 (327702/226465)
SMR: DU023-029
Excavation Licence No: N/A
Excavation duration/year: 1956 – 1959
Site director: G.D. Liversage (Research)
Excavations at Dalkey Island, during the latter half of the 1950s, revealed pre and contemporary
promontory fort activity dating to the early medieval period. The presence of large quantities of
imported B and E ware pottery demonstrates that the settlement was in use from the fifth to mid
seventh centuries. Prehistoric finds also indicate earlier use while historical records attest to
Scandinavian use of the site from the ninth century.
Dalkey Island is about eight hectares in size and is separated from the south Dublin coastline by a
fast-flowing tidal sound approximately 400m in width. A well supplies the island with fresh water. The
promontory fort is located on the northern side of the island and consists of a small headland cut-off
by a low bank with external ditch (Fig. 114). The fort is divided into two platforms by a low granite
cliff that runs from south to north. The western platform overlooks the harbour and the eastern
platform is between 2m and 3m higher.
The first excavation (termed Site II), between 1956 and 1958, investigated the promontory fort bank
and ditch on the lower western platform (Fig. 115). A possible entranceway was located consisting of
several postholes; two of which were stone-packed. Notably, a pre-bank occupation layer was
discovered and finds from the upper level included three bronze pins, B ware and E ware pottery
sherds, two glass vessel fragments, iron nails, a piece of worked bone, part of a broken whetstone
and part of a steatite ring. The lower fill contained only prehistoric finds. The presence of B ware and
E ware pottery beneath the bank indicates settlement activity, before the promontory fort was
constructed, between the fifth and mid seventh centuries.
The bank overlay the occupation layer and was approximately 1.5m high. Its related ditch was 5m
wide and between 2m and 2.4m deep. A number of hearths and burnt spreads were noted within the
ditch and were probably placed there to provide shelter from the weather. Two B ware sherds, iron
slag, two bone pins and three bone cylinders were retrieved from the ditch fill.
Liversage recorded a number of artefacts that were not stratigraphically related to the bank and
these included two sherds of Samian ware, a small bronze penannular brooch, a second possible
penannular brooch, a knife and two spindle whorls. The artefacts from Site II are indicative of
occupation even though no dwellings or related structures were identified.
A hearth and a possible cereal-drying kiln were revealed in the northern part of Site II but there was
no evidence for the bank and ditch here.
The higher, and more exposed, eastern platform was excavated between 1957 and 1958 (Site III).
The ditch and bank extended into this area although the latter was less substantial compared to the
findings at Site II. Site III revealed extensive early medieval evidence that included the remains of a
substantial sub-rectangular structure which was built upon the bank. The building measured
approximately 6m in length by 3.5m wide and contained a central hearth. The roof may have been
supported by the bank, or a ‘stone scatter’ which was not recorded on plan and may have functioned
as a low wall.
A sherd of Late Roman Amphora (B ware) was sealed beneath the hearth while a dark occupation
layer partially sealed the hearth and the rear slope of the bank. This contained animal bone, shell, a
glass bowl sherd, five sherds of E ware, a lignite or jet bracelet fragment, an iron loop-headed ringed
pin, nails, iron slag and a bone pin. A layer above this, that covered the bank, contained animal bone,
an iron ringed pin with an attached bronze chain, a bone pin, nails, worked bone and a hone stone.
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