[1] The original gatehouse was a simple affair, built in the late 13th century and known as the Saltmarsh Gate, as it led to marshlands outside the town.

[4][5] This spur enabled the town gunner to protect the sluices that controlled the flow of seawater into a tidal moat used to power the water mill under the tower.

The town gunner was also responsible for making the gunpowder and gunshot which he stored, together with the guns, in the gallery of the tower.

[7] The building stood empty until 1876, when it was requisitioned by the Southampton Harbour Board for use as storage, although the groundfloor of the gatehouse was retained for use as a mortuary.

[13] In 2019, God's House Tower reopened as an arts and heritage venue, with a permanent gallery about the history of the building, two new galleries showing contemporary art and important works from prestigious South Coast collections, access to the views from the roof and a branch of Hoxton Bakery.

[14] The short-lived Salisbury and Southampton Canal, which operated between 1802 and 1808, entered the River Test by way of a lock adjacent to God's House Tower.

From here, the canal followed a route just outside the town walls northwards until its junction with the Northam branch at what is now Palmerston Park.

[1] Under the main tower, the filled in arches of the tidal moat and sluices are visible on both the southern[17] and northern flanks.

[16] Opposite the gateway, in Winkle Street, is the only other remaining substantial part of the original hospital, the Church of St.