The Roman pharos or lighthouse was probably built in the first century A.D. A similar lighthouse was built on the Western Heights and at night guided Roman ships into the port of Dubris. The tower was octagonal outside and rectangular inside rising to a height of perhaps 80 feet (24m). It had eight storeys each set back 1 foot (0.3m) from the one below, which gave the whole structure the appearance of an extended telescope.Only the first four Roman storeys remain, the present topmost storey being a fifteenth century reconstruction. The present splayed shape of the pharos is a result of the severe weathering it suffers in exposed position and mediaeval refacing. In the late Saxon period when the church of St Mary-in-Castro was built the already ancient pharos became a free standing bell tower. The church was built in the late tenth or early eleventh century and reused much Roman brick in its construction. Cruciform in plan with a central tower and aisle less nave, it was considerably altered in the thirteenth century by Henry III. After the mediaeval period the church fell into ruin and was restored first in 1862 and then again in 1883 when the mosaics on the wall of the nave were added.