The Tower of Ayia Triada (Holy Trinity), called the Tower of Vasilis by the elder locals, is one of the most well-preserved ancient monuments in Amorgos. The Tower was most probably built during the 4th century B.C. and used to be a defensive structure. The tower took its name from the Byzantine church of Ayia Triada which is built nearby. The locals used the Tower to send fire-messages to other similar towers. It was the best way to exchange important messages from a distance. During the centuries, the building was used as a shelter for the farmers as well as storage space for their products.