All Hallows (meaning 'all saints'), which dates to AD 675, survived virtually unscathed by the Great Fire, only to be hit by German bombs in 1940. Come to see the church itself, by all means, but the best bits are in the atmospheric undercroft (crypt), where you’ll the discover a pavement of 2nd-century Roman tiles and the walls of the 7th-century Saxon church.
In the nave, note the pulpit taken from a Wren church on Cannon St that was destroyed in WWII and, by the south door, a Saxon archway and a beautiful 17th-century font cover decorated by the master woodcarver Grinling Gibbons. The church has two strong American connections: William Penn, founder of Pennsylvania, was baptised here in 1644 and schooled in what is now the Parish Room; and John Quincy Adams, sixth president of the USA, was married here in 1797. Free 20-minute tours depart at 2pm Monday to Friday from April to October.