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:Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.