Saint Thomas Tower was built above the shore on the seaward face of the headland of "il-Ħamrija" in Marsaskala. It is a substantial fortification intended to prevent the landing of troops in the sheltered anchorages of Marsaskala Creek and St Thomas' Bay. Construction of the tower was approved in July 1614, at the time of the raid of Żejtun, in which an Ottoman fleet managed to land at St Thomas' Bay. The tower was named after a chapel dedicated to St Thomas which stood close to where the tower now lies. It cost 13,450 scudi, 6 tari and 4 grani to build, making it the second most expensive Wignacourt tower, after Saint Mary's Tower.