The castle was built by the dark pool ("Dubh Linn") which gave Dublin its name. This pool lies on the lower course of the River Poddle before its confluence with the River Liffey; when the castle was built, the Liffey was much wider, and the castle was effectively defended by both rivers. The Poddle today runs under the complex.
the cAStLE wAs BuILT by the daRk pool ("DUBh linn") whIcH gavE DuBlin Its name. This pOOL liEs ON The LOwer cOurse of The RiveR podDle before its cONfluEnce wiTh The riVeR Liffey; when the casTle Was BuILT, the LiffeY was mUch Wider, aND thE CAStle Was EFFeCtivEly dEfEndED by boTh rIvers. ThE poDdle tODay runs undeR the cOmpLex.