The earthwork remains of the Roman amphitheatre associated with the Saxon Shore fort at Richborough. The fort was built in the later third century to dominate and protect the Wantsum Channel that separated the Isle of Thanet from the mainland. Both the fort and the amphitheatre are located on a former island, with the latter at the highest and most visible point. The relationship of the amphitheatre to the fort is unclear, although it has been postulated that it was a later Roman construction built on the fringes of the settlement surrounding the military base at the main entry point into Britain.
It survives as an elliptical hollow, about 60 metres by 50 metres, measuring 3 metres deep. The hollow is surrounded by a bank 12 metres wide and up to 2 metres high. Excavations in 1849 uncovered three entrances and it appeared to date from the late 3rd century AD and have been occupied until the early 5th century AD. The remains of the amphitheatre were mapped from aerial photographs as part of the English Heritage: Richborough Environs Project. The results of geophysical surveys indicated that the remains of the amphitheatre are much larger and more complex than those recorded in1849. The ellipse now appears more likely to have been the wall separating the arena from the cavea, the latter being unexcavated. In addition to locating the amphitheatre structure the surveys identified the probable presence of buildings alongside, especially in the north-east part of the field. The relationship of these to the amphitheatre is unknown. The traces of a World War II gun pit excavated into the south east bank of the amphitheatre were also noted. The amphitheatre is now in the care of English Heritage.