The visible remains of an amphitheatre constructed during Roman London lie beneath Guildhall Yard in the City of London. Some of these remains are displayed in situ in a room in the basement of the Guildhall Art Gallery complex. Discovered in 1988, the site is now a scheduled monument.
London's first Roman amphitheatre was built in AD 70 from wood, but was renovated in the early 2nd century with tiled entrances and rag-stone walls. The amphitheatre was used for various public events such as gladiator games, entertaining soldiers and the public with animal fighting and public execution of criminals, as well as religious activities. After the ancient Romans left in the 4th century, the amphitheatre lay derelict for hundreds of years.
Wikipedia https://en.wikipedia.org/wiki/Amphitheatre_(London)
Address 87 Gresham Street, City of London EC2V 7, United Kingdom
Coordinates 51°30'56.14" N -0°5'31.505" E