The Black Pool of Dublin

The Dubhlinn Garden south of Dublin Castle is the location of a tidal pool in the River Poddle, a tributary of the River Liffey. The city takes its English and international name from this ‘black pool’.


The original settlement called Dubhlinn took the form of a Gaelic monastery due south of the pool in what is now the Aungier Street district. This was a typical enclosure site, still partly preserved in the pattern of streets focused on medieval St Peter’s Church. Its first recorded abbot, Bearaidh, died in 656 and shadowy bishops are also documented.

The pool may have functioned as a small port of call for monks who needed wine for liturgical purposes, though of that we have no direct evidence. Unlike at neighbouring monastic sites such as those at Clondalkin, Swords and Tallaght, we have to assume that monastic life ceased at Dubhlinn in 841 when it was taken over by pagan Vikings.

The usefulness of the tidal pool as a shelter for their fleet of warships meant that Vikings called the place Dyflinn, from the (modernised) Irish Dubhlinn. Their first longphort, ‘ship harbour’ was probably located on the south side of the pool, where a small number of early burials have been found.

Soon afterwards, however, a more defensible second longphort was established on the north side of the pool. Houses and other structures dating from the late ninth century have been found at Essex Street West. For trading purposes, this may have been the location of Dublin’s first commercial port.

The pool site has never been excavated archaeologically, but it is likely that it contains the remains of shipbuilding and ship repair. One ship, known as Skuldelev 2 and built probably in Dublin in 1042, was found deliberately scuttled in Roskilde harbour in Denmark. A replica called The Sea Stallion from Glendalough was sailed with a crew of sixty volunteers from Roskilde to Dublin in 2007.

Down to the late twelfth century, the black pool itself probably served as the main base for Dublin’s fleet of warships. As late as the 1160s King Henry II of England hired this fleet in an unsuccessful expedition to Wales.

After the Anglo-Norman takeover of Dublin in 1170 the Poddle was partly redirected along Patrick Street and adapted as a moat for the castle. This was made possible by damming the river at what we call Dame Street (really ‘dam street’), so that the pool became a remnant of its former self. It can be seen in this form on the earliest surviving map of Dublin, engraved for John Speed in 1610.

Nevertheless, names in this locality were formed to reflect proximity to the pool. These are the Pool Gate in Werburgh Street, the Pool Mill just outside and the church of St Michael le Pole in Ship Street. Misleadingly named, incidentally, the real name of the latter should be Sheep Street, as it was in the Middle Ages.

Because the ground was wet and salty, this land was never used for farming or built on throughout centuries of continuous urban development. As a result, we can still enjoy its presence and memory today as a public park.