The ruins of city walls
In 2017 London is a sprawling metropolis that expands year after year, but that wasn’t the case in Roman London. A solid stone and red tile wall, built in AD 200, enclosed the city of Londinium in its entirety, stretching for two whole miles. It was basically the Roman equivalent of the M25. You can still spy small sections of the original wall by the Museum of London and the Tower of London. London Wall. Tube: Tower Hill and Barbican.