Dublin Castle Ireland (1800–1922). After the signing of the Anglo-Irish Treaty in December 1921, the complex was ceremonially handed over to the newly formed Provisional Government led by Michael Collins. It now hosts the inauguration of each President of Ireland, and various State receptions. 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
Transport in Dublin Dún Laoghaire harbour from both Malahide and Howth in the north which en route to Dún Laoghaire goes straight the city centre. It is also served from Greystones in the south. Both domestic and international air traffic in Dublin is served by Dublin Airport which is located 10 km north of Dublin city centre in Collinstown and is accessible by car or bus. It is the busiest airport by far in Ireland with 27.9 million passengers in 2016, making it the 15th busiest airport in Europe with flights to other airports in Ireland, Europe, North America, Africa and the Middle