Museum of London
Londinium was a settlement established on the current site of the City of London around AD 43-50. It sat at a key crossing point over the River Thames which turned the city into a trading port, serving as a major commercial centre in Roman Britain until its abandonment during the 5th century.
Sometime between 190 and 225, the Romans built the London Wall, a defensive ragstone wall around the landward side of the city. The London Wall was one of the largest construction projects carried out in Roman Britain, requiring somewhere in the region of 85,000 tons of Kentish ragstone to complete.
Once built, the wall was 2 miles long and about 6 m high. Until the later Middle Ages, the wall defined the boundaries of the City of London.
Parts of the wall are still visible across the City of London boundary line today. Starting at Tower Hill, going north to Aldgate and Bishopsgate. From there turn West and head along the north side of the wall, past Moorgate, Cripplegate and West Cripplegate. Finally heading South towards Newgate, Ludgate and Blackfriars