Bač Fortress is important monument of culture of the impressive Medieval fortress in the northern part of Serbia, in the Backa district of Vojvodina. The Bac Fortress is the cultural monument of outstanding significance for the Republic of Serbia. It is located near the town of Bač, all built on the Mostonga river meander, approachable only along the bridges. Bač is the center of the Bac Municipality which comprises six settlements, 62 km away from Novi Sad and 140 km from Belgrade. The municipality of Bač is a border town on the left bank of the Danube River, and its western border with the Republic of Croatia.
Bac Fortress has been built at the time of Hungarian King Charles Robert I /1310–1342/. Then there were eight towers, various chambers of the county manager, corridors, spaces for guards, kitchen, well, barn, etc.. Bač Fortress soon became an important military, political, cultural and ecclesiastical seat and its tower has served as an important part of the defense system of the fortress, but also as an observation post. Since the time of the Mohács battle in 1529, the city and fort came into the Turkish rule. From this period dates the descriptions of the Backa fortress in itineraries of Evlia Ćelebia. According to traveler description the city was surrounded by a wide circle of trenches filled with water. From the time of Rákóczi Rebellion /1703–1711/ Bac fortress was burned, destroyed and abandoned. At the beginning of the 20th century the monastery was taken over by the Franciscans from the province of St Ivan Kapistran from Hungary. The poverty of the brotherhood contributed to the preservation of the stylistic purity of the former phases in building, which caused the planned and anticipated neo-stylistic reconstruction in 1908 not to happen. After 1923, the monastery in Bač belonged to the Croatian province of St Cyril and Methodius because the borders had been changed and Yugoslavia /the Kingdom of the Serbs, Croats and Slovenians/ was formed in 1918. After the Second World War, the Protection Service evaluated and protected the monastery by a law in 1951. However, the Bač fort remained the best preserved medieval fortress in Vojvodina. In Bač today there are the ruins of the former fortress whose base is in the form of an irregular pentagon. In the ruins of the Bac fortification there are four lateral and one central tower height of 18 meters, which was partially reconstructed.
The Franciscan Monastery in Bac is a rare and outstanding heritage site in Serbia. It is located in the center of Bač, in the southwest of Bačka district, which was named after this ancient town. The Franciscan Monastery complex sits well within the landscape and the medieval matrix, with a 45-metretall bell tower. The Church of the Assumption of Virgin Mary features one narrow and long nave oriented towards the east-west direction, and a five-sided apse and altar on the east. The church is appended on its south side by a massive and tall bell tower reinforced with angled counter forts. Cruciform vaults, reinforced with Gothic stone ribs, are attached to the pilasters’ vault the three spaces of the naos in the width of the altar. The rest of the church nave is vaulted with semi-circular vaults and along the north-west side of the church two counter forts were built. The middle of the north wall was opened in three places to make the access to the added chapels covered with a single roof. When carrying out the research and conservation works, a Mihrab niche was discovered in the south wall. It testifies to the times when, during the Turkish rule, the church was converted into a mosque. In the upper area of the church, there is a choir with an organ dating from 1827. The recognizable monastery complex in the shape of a square with an inner yard is made up of the church of the Assumption of Virgin Mary with a bell tower added along its west side and three one-floor wings built on its south side. The present-day Franciscan monastery complex evolved during a long period of six centuries. Its complex structure is made up of Romanesque, Gothic, Renaissance, Islamic and Baroque architecture. The rich treasury, old books, paintings, sculptures, liturgical robes and inventories testify to the life of this cult place.
The monastery was renovated in phases during the 18th century, possibly on the remains of an older monastery buildings, which needs to be confirmed by the archaeological research. On the ground floor, there are common rooms /Franciscan room, laundry, kitchen, brewery, refectory/ linked by a hall. On the first floor, there are numerous rooms where old furniture, inventory and liturgical robes are kept. The hall from which they entered the rooms used to be an open one. Special attention is be paid to the library where, beside the rare and valuable books, there are registries, music books and a credible model of the monastery. During the Baroque renovation of the Franciscan monastery in Bac, the exterior shapes of the church and the dormitory were being equalized, which caused considerable changes to the exterior façades of the church. When equalizing the height of the objects of the complex, the apse was extended. Thus, the authentic and picturesque Romanesque-Gothic surfaces built of brick and stone, with narrow windows, were considerably changed, which lessened their value. The rest of the façades were plastered. Along the west gable, a portal and an attic, shaped according to the principles of the Baroque architectural style, were added.
During the long period of its existence, the Franciscan monastery in Bac has been threatened by humidity. The threat is not only the high level of underground water, but also the problem of the rainwater drainage system that has not been solved yet. There are no pavements around the objects. Water breaks through the basements and the crypt, it then rises and damages the building materials, especially the bricks and the works of art. The monastic community consists of only a single friar! The number of people who sustain the monastery is constantly decreasing. Unless there is more help, it will not be possible to sanitize the damp walls or to open the gates of the monastery for visitors. In 1965 The Provincial Institute for preservation of cultural monuments compiled documentation of the existing condition, while archaeological excavations inside the church and on the outside of the altar were also carried out. The conditions for the preservation of the complex and the protected surroundings have been incorporated in the spatial plan of the Municipality of Bač (the plan is being drawn up) and the general plan for the regulation of Bač. The development project of integrative protection of the heritage of the municipality of Bač “Bač through history” treats the Franciscan Monastery as one of the four most important cultural assets, along with the medieval fortress, the Orthodox monastery of Bodjani and the Turkish bath – hammam.