The Petrovaradin Fortress, also known as ‘Gibralter on the Danube’ is located on a rocky hill opposite today’s Novi Sad city centre. Because of its dominant geographical position, many people, namely the Celts, the Romans, the Avars, the Byzantines, the Hungarians, the Turks, and, ultimately, the Austrians, who built the fortress we know today in XVIII century, badly wanted to conquer it for centuries. Petrovaradin is a very well-preserved and is the second largest fortress to be found in Europe. It is considered to be one of the best achievements of the European military architecture of XVIII century. Its strong and thick defending walls are made of brick and were built for the purpose of fighting with powerful fire-arms and encompass the upper and the lower garrison city coming out onto the Danube banks. The underground of the fortress consists of a tangle of the underground tunnels, galleries and corridors, while the army barracks once intended for the accommodation of officers and soldiers with an arsenal, a number of workshops and other buildings whose once defensive role has since been replaced with cultural and tourist attractions, including many art galleries and are surrounded by the thick walls. The Observatory and Historical Archive have found their place inside the fortress. The gunboat has been transformed into the Museum of the City of Novi Sad, and in one of the barracks there is a hotel, while numerous studios have since opened in the cellars. The baroque tower with a big clock on the Ludvig bastion is the fortress’s recognizable tourist attraction and affords the visitor with a magnificent view of the Danube and Novi Sad.