The ground around Dublin Castle is where the city began, on the ridge above the dark pool, the dubh linn, that gave Dublin its name. The castle itself was the seat of British rule in Ireland for seven centuries and now hosts state ceremonies; its State Apartments and the small but dazzling Chester Beatty Library of manuscripts and Islamic art are both well worth a visit.
Nearby rise the city's two medieval cathedrals. Christ Church, with its atmospheric crypt, and St Patrick's, the largest church in Ireland and once home to Dean Jonathan Swift, stand within a short walk of each other on the higher ground of the old town.
The surrounding streets, between the castle and the river, are among the oldest in Dublin and reward wandering, with the Wood Quay heritage area and the City Hall rotunda close at hand.