Opposite the Ostrovica burg, across the river Una valley and the town of Kulen Vakuf, there are remnants of the old burg of Havala. Havala was built around XVII century, probably by Sultan Ahmed III.
This burg consisted of stony gates and one tabija, and its eastern side was surrounded by five meter high and one meter wide wall. Concluding on a still visible mihrab, upon the main entrance gate there was a mesdžid, and to the left form the entrance there were two towers. Throughout the centuries Havala was a strategically important fortification, overseeing the bridge over the Una, Kulen Vakuf and the roads on the right side of the river which connected Lika and Dalmatia with other parts of the wider region.
To the west of Hvala there is a Muslim graveyard with the tombstone of Smail-beg Kulenović, who was one of the dizdars (commanders) of the Havala burg. The tombstone has a form of a sarcophagus with two vertical grave stones – nišans and it is hewn is local bihacit stone which is very long-lasting and suitable for stone carving. Despite long being neglected, writings in Arabic letters and Turkish language are still visible and readable.
 Tabija - Arabic word for fortification which can accommodate soldiers.
 Mihrab is a semicircular niche in the wall of a mosque that indicates the qibla; that is, the direction of the Kaaba in Mecca and hence the direction that Muslims should face when praying. While praying, the imam (priest) of the mosque is in the mihrab, whereas all the others are behind him.
 Mesdžid – a room (temple) for praying.