Silchester was originally the centre of the Iron Age kingdom of the Atrebates tribe from the late 1st century BC. After the Roman conquest in AD 43 it developed into the town of Calleva Atrebatum. Laid out on a distinctive street grid pattern, the town contained many public buildings and flourished until the early Anglo-Saxon period. Unusually among the Roman towns of southern Britain, it was not abandoned until the 6th or 7th century.
This 360 is taken as sun beginning to set in the south, upon the northern wall.