If you're looking for a turreted castle straight out of central casting you'll be disappointed: the stronghold of British power in Ireland for 700 years is principally an 18th-century creation that is more hotch-potch palace than medieval castle. Only the Record Tower, completed in 1258, survives from the original Anglo-Norman fortress commissioned by King John from 1204.

The castle is now used by the Irish government for meetings and functions, and can be visited only on a guided tour of the State Apartments and of the excavations of the former Powder Tower.

The castle was officially handed over to Michael Collins, representing the Irish Free State, in 1922, when the British viceroy is reported to have rebuked Collins on being seven minutes late. Collins replied, 'We've been waiting 700 years, you can wait seven minutes.'

As you walk into the grounds from the main Dame St entrance, there's a good example of the evolution of Irish architecture. On your left is the Victorian Chapel Royal (occasionally part of the Dublin Castle tours), decorated with more than 90 heads of various Irish personages and saints carved out of Tullamore limestone. Beside this is the Norman Record Tower with its 5m-thick walls. It's currently closed to the public pending a long-awaited revamp. On your right is the Georgian Treasury Building, the oldest office block in Dublin, and behind you, yikes, is the uglier-than-sin Revenue Commissioners Building of 1960.

Heading away from that eyesore, you ascend to the Upper Yard. On your right is a figure of Justice with her back turned to the city, an appropriate symbol for British justice, reckoned Dubliners. Next to it is the 18th-century Bedford Tower, from which the Irish Crown Jewels were stolen in 1907 and never recovered. Opposite is the entrance for the tours.

The 45-minute guided tours (departing every 20 to 30 minutes, depending on numbers) are pretty dry, but you get to visit the State Apartments, many of which are decorated in dubious taste. You will also see St Patrick's Hall, where Irish presidents are inaugurated and foreign dignitaries toasted, and the room in which the wounded James Connolly was tied to a chair while convalescing after the 1916 Easter Rising, so that he could be executed by firing squad.

The highlight is a visit to the medieval undercroft of the old castle, discovered by accident in 1986. It includes foundations built by the Vikings (whose long-lasting mortar was made of ox blood, egg shells and horse hair), the hand-polished exterior of the castle walls that prevented attackers from climbing them, the steps leading down to the moat and the trickle of the historic River Poddle, which once filled the moat on its way to join the Liffey.

There's a self-guided tour option, but that only includes the State Apartments.