Kaštilac was a fortress of a Benedictine Monastery. Kaštilac is the only castle of seven castles in Kaštela. King Zvonimir of Croatia of the Svetoslavić branch of the House of Trpimirović, had donated to a Benedictine from Split possession in the Kaštela field (Kaštelansko polje) in 1078. In the 12th century Benedictine built a church of St. Cosmas and Damian in the Romanesque Architecture style.
Due to the Turkish threat, Benedictine nuns completed the construction of a fortified settlement Kaštilac on the islet of Gomilica in 1545. Entrance to the castle is protected by high tower over the stone bridge with arches. Kaštilac is 40 metres away from the shore, connected with the stone bridge, which was made only of stone. Fortress has square floor plan and in the past, at the entrance was located drawbridge. After the fortress was completed, within the fortification walls arrived inhabitants of the Upper and Lower Kozica, after the Turks had devastated their former villages. In the 17th century the tower lost its defensive function.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.