London’s roots lie in the walled Roman settlement of Londinium, established in AD 43 on the northern banks of the River Thames, roughly echoing the dimensions of today’s City. Few traces of the 2nd-century Roman wall survive, although post-Blitz demolitions uncovered a section running along Noble St. You can glimpse the remains of a bastion between the Museum of London and the Barbican, and other sections near Tower Hill tube stop and within the grounds of the Tower of London.