The Angevine-Aragonese castle of Gallipoli dates back to the 13th-14th centuries, but the town used to have a stronghold already during Roman time, together with towers enlarged by the Byzantines and by the Normans. The Angevins and the Aragonese modified the structure of the fortress, but Francesco di Giorgio Martini was the one who made important changes. During the 19th century the moat was filled up and the arches which used to support the lift bridge were filled in.
The fortress has a square base strengthened by the four towers. The tower Vedetta, topped by merlons, has a polygonal shape. The other towers are surrounded by a string course and are decorated with small arches. The eastern curtain, the Rivellino, is a fifth circular tower separated from the rest of the walls and has not been renovated yet. Inside it, there are large rooms with barrel and cross vaults.
References:Celje Castle was once the largest fortification on Slovenian territory. The first fortified building on the site (a Romanesque palace) was built in the first half of the 13th century by the Counts of Heunburg from Carinthia on the stony outcrop on the western side of the ridge where the castle stands. It had five sides, or four plus the southern side, which was a natural defence. The first written records of the castle date back to between 1125 and 1137; it was probably built by Count Gunter. In the western section of the castle, there was a building with several floors. Remains of the walls of this palatium have survived. In the eastern section, there was an enclosed courtyard with large water reservoirs. The eastern wall, which protects the castle from its most exposed side, was around three metres thicker than the rest of the curtain wall. The wall was topped with a parapet and protected walkway.