This tower was built in 1659 and was one of a series of watchtowers located around Malta. There were thirteen of these towers built under the instruction of Martin de Redin, the Grandmaster of the Knights of the Order of St. John. The towers aren’t doing too badly, as eight of them are still intact, two are partly intact and only three have been lost to history.
Bits of the tower started to fall off recently, but it has been repaired internally and a new staircase added. The entrance is visible above and access would have been gained via a retractable ladder. To my knowledge there’s no way of visiting the inside of the tower.