St. Nicholas' Fortress was built on the left side at the entrance to St. Anthony Channel, on the island called Ljuljevac. The island is situated at the entrance to the Šibenik channel across the Jadrija beach lighthouse. St. Nicholas' Fortress got its name from the Benedictine Monastery of St. Nicholas, which was originally on the island, but due to the construction of the fortress, it had to be demolished. At the request of domestic Croat population of Šibenik, the Venetian captain Alojzije de Canal decided to build a fort on the island of Ljuljevac in 1525. The fortress was designed and built by the famous Venetian architect and builder Hyeronimus di San Michaela. It was built by in the 16th century to prevent Turkish boats from reaching the port. St. Nicholas' Fortress was armed with 32 cannons. However, its imposing appearance and size were a bigger threat to the enemy than cannons ever were.
The fortress is one of the most valuable and best preserved examples of defense architecture in Dalmatia. It is made of brick because that material was considered to be most resistant to cannonballs, while the foundations are made of stone. Although defense capabilities of the fortress have never been tested in military operations, the structure still proved successful in protecting the city from sea-bound enemy attacks. During the centuries of use, the structure served to various armies and has undergone a number of renovations, some of them necessary only because of the development of arms. It was completely abandoned by the military in 1979 and has been undergoing renovation ever since.
St. Nicholas' Fortress was included in UNESCO's World Heritage Site list as part of 'Venetian Works of Defence between 15th and 17th centuries' in 2017. After reconstruction work that lasted for two years, the fortress was open to visitors in July 2019.
References:The Château du Haut-Koenigsbourg is situated in a strategic area on a rocky spur overlooking the Upper Rhine Plain, it was used by successive powers from the Middle Ages until the Thirty Years' War when it was abandoned. From 1900 to 1908 it was rebuilt at the behest of the German kaiser Wilhelm II. Today it is a major tourist site, attracting more than 500,000 visitors a year.
The first records of a castle built by the Hohenstaufens date back to 1147. The fortress changed its name to Koenigsburg (royal castle) around 1157. The castle was handed over to the Tiersteins by the Habsburgs following its destruction in 1462. They rebuilt and enlarged it, installing a defensive system designed to withstand artillery fire.
The fortification work accomplished over the 15th century did not suffice to keep the Swedish artillery at bay during the Thirty Years War, and the defences were overrun.