Osor developed in the area where the islands of Losinj and Cres came closest. The town is known as a museum town and has always been one of the leading town centers of the islands of Losinj and Cres. The settlement experienced its greatest prosperity in the ancient era.
In the past, the main transit traffic between the Dalmatian coast and the Northern Adriatic took place here, which it enabled dug canal (Kavuada, Cavata, Cavanella). Osor was an international port in that period. The ancient town square contains buildings from the 15th and 16th centuries, such as the town hall with a covered loggia, the former town cathedral with a bell tower, the former water reservoir and the bishop's palace. The picturesque square represents the historical center of Osor. Today, the Losinj Museum - Osor Archaeological Collection is housed in the building of the former town assembly. The Renaissance one-story building was built in the first half of the 15th century. It has been protected as a cultural monument since 1964. The collection was opened to the public in 1889.
The spacious loggia houses a lapidary containing Roman inscriptions, architectural stone decorations, a Renaissance lintel with coat of arms and Renaissance inscriptions. On the first floor, mostly objects from the period of the early Roman Empire are exhibited. Based on these finds, the visitor can imagine everyday life in Osor in those times.