The stronghold of British power in Ireland for 700 years, Dublin Castle is mostly an 18th-century creation built on Norman and Viking foundations. Of the 13th-century Anglo-Norman fortress built on the site, only the record tower remains. Once the official residence of the British viceroys in Ireland and now used by the Irish Government, a tour will appeal to history and architecture buffs. On Sunday and holidays free tours run every 30 minutes. Please note that the State Apartments may be closed at short notice – call ahead to check.