Perfect for the mechanically-minded, these behind-the-scenes tours take visitors to the inner sanctum of the world's most famous bridge and include access to areas that are normally out of bounds to the public. Tours are divided into two parts. First, you'll get a history of the bridge and its construction while exploring the building, its walkways and engine rooms. The second part of the tour is conducted by one of the bridge's technical officers, who takes visitors to the Bridge Control Room, the Bascule Chambers below the level of the river bed and the Machinery Room, housing the hydraulics that power the lifting of the bridge. Tours last two hours and are not suitable for under-12s. Booking is essential via the ticket hotline – 020 7407 9191 – or by emailing email@example.com.