Archaeological excavations of the area in 1962-1963 suggest that the original settlement was centred to the east of St Peter's Church, with Mary-le-Port on its western limit. The building of Bristol Castle in the latter part of the 11th century resulted in the focus of the settlement being moved to the west, where it developed into a symmetrical plan centred on the crossroads of High Street, Wine Street, Broad Street and Corn Street. The area around Mary-le-Port Street was thus the most ancient part of the mediaeval city. Bristol Castle was home to the Norman garrison, and was a massive structure whose keep was comparable to that of the Tower of London. The castle occupied the whole of the eastern end of today's Castle park, from just east of St Peter's Church to Lower Castle Street.