The remains of the medieval fortified towns Zvecaj, Greben and Bocac are on the tops of hills along the river Vrbas and the main road that connects Banja Luka and Jajce. These fortresses, which date between the 12^th and 15^th century, were used for the defense of the Vrbas valley from enemy assault. Viewpoints provide a special attraction, near the fortifications, from which a fantastic view stretches over the valley of the Vrbas River and its canyon.

Medieval town Greben
The medieval fortified town greben is located in Krupa na Vrbasu, 25km south of Banja Luka. It was first mentioned in sources in 1192, and then in 1322 and 1346, when the city was controlled by a certain Nikola. In the 14^th century, Greben was in possession of feudal lords Hrvatinic, lords of Donji Kraji, as evidenced by charters signed, in this city in 1374 and 1375. The town was destroyed during the taking of the Jajce Banovina by the Turks from 1527 to 1528, and in Turkish sources it was referred to in 1562, in the area of the Jajce nahiye and under the names Greben and Vrh Krupa. It seems that in the period of Turkish rule, the town was abandoned. Today, it is in ruins. A little better preserved is only the tower above Vrbas and part of the walls that descend to the canyon of the river.

Medieval fortress Bocac The fortress Bocac is located on the left bank of the Vrbas River, in the middle of the road E661, between Banja Luka and Jajce. It was built at the beginning of the 15^th century with the task of defending the crossing over Vrbas. It is first mentioned in a charter from 1448. It was town from 1463 to 1527, when it fell to the Turks it was a fortification of the Jajce Banovina. In the early eighteenth century, Bocac was mentioned as a fortress with a small number of cannons. It was abandoned before 1833. During the Turkish occupation, it was subsequently fortified and maintained, so even today its strong walls and towers surrounding a spacious town garden are relatively well preserved.

The medieval fortified town Zvecaj
The remains of the medieval fortified town Zvecaj are located about 10 kilometers south of Banja Luka, on the southern slopes of the cliff above the left bank of Vrbas. Zvecaj was first mentioned in 1404, when Duke Hrvoje Vukcic signed a contract here with the people of Dubrovnik against the Bosnian king Ostoja. It is assumed that this fortification is older than that occasion. In 1419, the Bosnian king Stjepan Ostojic confirmed the privileges of Dubrovnik in Zvecaj. In 1463 the Turks took the fortification, and at the end of the same year it was taken over by the Hungarian army of Matija Kovin, and in 1527 it was handed to the Turks by captain Andrija Dresneki, it served as a fortress of the Jajce Banovina. The town consisted of a citadel, walls that descend towards Vrbas and towers, one of which is preserved to a height of about ten meters.