The medieval town Rmanj was built in late 14th or early 15th century at the mouth of Unac into Una, and there are opinions of historians that this ancient city dates from the 12th century. According to records from the year 1396 this town was called Konuba. The town walls were demolished to the ground, and the only thing kept is the round tower about 10 meters high, that has levels separated by arches. It is first mentioned in 1431 when the Hungarian king Sigismund pledge it to Nikola Frankopan. In 1436, widow Anža Frankopan, lived in Rmanj for a while and signed herself as a princess Rmanjska.
In the mid 15th century Juraj Frankopan got it. In 1451, ''judge'' and "brotherhood purgar" is mentioned in this town. Titled Rmanj, this city is mentioned in 1504 among the cities that had to be repaired and better established.