The Square Tower

The Square Tower is a fortification and former Governor's residence, now a museum, dating from circa 1494. The building has undergone substantial alteration, notably to create a powder magazine circa 1580 and later as an Admiralty Victualling store circa 1780. It was reinstated as part of the fortifications in the mid-19th century and restored between 1978 and 1985. The structure is built of stone and brick, with a flat stone-paved roof. Three restored 19th-century gun races face south-west.

The south-west part of the exterior is one storey, while the north-east part is two storeys high, comprising two bays. The main entrance, which faces south-east within an enclosed yard, features a late 20th-century replica of the original 18th-century doors. These doors have lower panels and vertical iron bars to the upper panels, set under a segmental stone arch with rusticated voussoirs and jambs. A mid-18th-century two-leaf 20-pane casement window is located on the first floor. A late 20th-century boarded door, providing access to the roof area, and a visitors’ viewing balcony are positioned at saluting platform level. The north-west facade has a late 20th-century boarded door set within a 15th-century opening, along with an 18th-century two-leaf casement within a 15th-century opening. A replica of the original 18th-century panelled door, with vertical iron bars to the top panel, is located further to the right. The first floor has a mid-19th-century two-leaf 4-pane casement on the left and a late 20th-century glazed infill on the far right. On the north-east side, facing Broad Street, there is a niche edged with a wreath, containing a late 20th-century replica of a gilded lead bust of Charles I by Hubrecht le Sueur. Below the bust are the Royal Arms, and an inscription reading: "After his travels through all France into Spain and having passed very many dangers both by sea and land he arrived here the 5th day of October 1623”.

The late 20th-century restoration revealed Tudor features, including two fireplaces, and 18th-century features, such as a stone stairway on the north-east side, running from the ground floor to the former basement.