Guildhall Art Gallery

Bang in the centre of the Square Mile, the Guildhall has been the City's seat of government for nearly 800 years. The present building dates from the early 15th century, making it the only secular stone structure to have survived the Great Fire of 1666, although it was severely damaged both then and during the Blitz of 1940. Most visitors' first port of call is the impressive Great Hall, where you can see the banners and shields of London's 12 guilds (principal livery companies), which used to wield absolute power throughout the City. It is often closed for various other formal functions, so it's best to ring ahead.Beneath the Great Hall is London's largest medieval crypt, with 19 stained-glass windows showing the livery companies' coats of arms. The crypt can be seen only as part of a free guided tour (tel: 7606 3030, ext 1463).The buildings to the west house Corporation of London offices, the Guildhall Library, and the Clockmakers' Company Museum (7332 1868; Guildhall Library, Aldermanbury EC2; admission free; ;09:30-16:45 Mon-Fri), which has a collection of more than 700 clocks and watches dating back some 500 years. The clock museum sometimes closes for an hour or two on Monday to wind the clocks.