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.

[1] 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.

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.