London’s roots lie in the walled Roman settlement of Londinium, established in 43 CE on the northern bank of the River Thames. Few traces of the 3rd-century Roman wall survive, but post-Blitz demolitions uncovered this section along Noble St. The scant brick and stone wall remains aren't the most evocative and are put into better context by first visiting the nearby Museum of London.
You also can glimpse the ruins of the Roman fort gate to the north, across the aptly named street, London Wall. Other sections of the wall are visible near Tower Hill station and within the grounds of the Tower of London.