This eminence on the southern banks of the Boyne, possibly an ancient passage grave, was crowned by an Anglo-Norman motte and then by 18C fortifications. From the highest spot, there is a beautiful view of the city centre and of the railway viaduct, which was built across the estuary in 1855. Until then passengers travelling between Dublin and Belfast by rail had to be transferred by stagecoach from the south bank to join another train on the north bank.