Issa was an island town and the most important Greek colony in Croatia. Its foundation is associated with the colonizing efforts of Dionysius the Elder in the first half of the 4^th century BC. It was situated in the very heart of the Adriatic Sea, on the island of Vis.

The town was built on Gradina Hill by the island’s deep bay, which was formerly called St. George’s Harbour. Inside its walls, the terraced city descended to the sea, and it was sub-divided by numerous north-south streets (stenopoi) and a smaller number of east-west streets (plateiai), which created a uniform urban layout of residential neighbourhoods.

The city was girded by ramparts made of large stone blocks, which gave it a slightly trapezoidal shape. As an island town and port, Issa had a sturdy waterfront quay also made of immense stone blocks that can still be seen under the sea in the southern part of the town and at places around Prirovo Peninsula.

The necropolises were located outside the city, close to the eastern and western ramparts. They are dominated by graves made of large stone slabs that were vertically laid into the ground so that they form a stone chambers.

During the civil war in Rome in the mid-1^st century BC, Issa sided with Pompey against Caesar. The conflict partially spilled over into the Adriatic, where after the battle at the island of Šćedro, Pompey’s fleet was defeated and Issa lost its independence in 47 BC. Nevertheless, Issa continued to prosper even after the advent of Roman rule, which was best reflected in the extent of its development. Thus, public baths were built over a rather large area in the southern part of the city near the seashore. So far, the following sections of the baths have been defined: the caldarium, tepidarium, frigidarium, prefurnium, apoditerium and a storage room.

Drusus, the son of Emperor Tiberius, resided in Issa at around 20 AD, and he had a training ground built there. We know this thanks to an inscription found in Issa (on display in the stone monument collection of the Archaeological Museum in Split), and his stay in Illyricum, “in order to inure him to war, and gain him the affections of the army,” was confirmed by Tacitus.

Issa once more appears in the sources with reference to the events surrounding the attempted rebellion against Emperor Claudius. In 42 AD, the consul of the Roman province of Dalmatia, Lucius Arruntius Camillus Scribonianus, with the help of several senators, staged a revolt that was quickly crushed. He then fled to Issa, where, according to Tacitus, he was slain by the soldier Volaginius.

Besides the aforementioned buildings, Issa also had a portico on the side of the town facing the sea. This is confirmed by an inscription mentioning that it had been restored by Quintus Numerius Rufus, who was the in plebeian tribune in Rome in 56 BC.

The Issaean theatre was probably built in the 1^st century on Prirovo Peninsula. It had a southward orientation, although its remains are not fully visible today because in the Conventual Franciscans built a monastery over it in the 16^th century.

The history of Issa during Late Antiquity and the early Middle Ages is a great unknown, because there are not many written sources nor material remains, which is a consequence of insufficient research. It was mentioned in the work Ethnica by Stephanus of Byzantium in the 6^th century, while in the 10^th century it was mentioned by both John the Deacon and Constantine Porphyrogenitus.

The Issa Branch Collection is located in Vis, in the Our Lady’s Battery (Gospina Batarija) Fortress, built for the needs of the Austrian authorities at the beginning of the 19^th century. The collection contains over 4,000 items, accounting for a wealth of prehistoric, Hellenistic and underwater archaeological materials. It was created as a result of archaeological excavations in the territory of ancient Issa, and on the rest of the island of Vis, as well as the nearby islands of Biševo, Svetac and Palagruža and in the waters surrounding them. Materials and entire collections were also purchased, while some of the items were donated.

When the Issaean materials were part of the Classical Antiquity Section of the Archaeological Museum in Split, it was under the supervision of Mladen Nikolanci, and then Branko Kirigin after 1984, when the Greco-Hellenistic Collection was established. Issa has been classified as a museum site in the Charter of the Archaeological Museum in Split since 1988. The word collection was added to its name in the Charter of 1996. Boris Čargo became the first curator of the independent Issa Branch Collection and Site.

In 2005, the Croatian History Museum in Zagreb handed over various documents testifying to recent and contemporary Croatian history, weapons and objects from the contemporary history of Vis to the Issa Branch Collection. The ceremony was attended by officials from the Croatian Ministry of Culture and staff members of the Croatian History Museum and the Archaeological Museum in Split. These items were formally transferred to the Archaeological Museum in Split, for the purpose of exhibiting them in a suitable facility, thus enriching the museum display in the Our Lady’s Battery Fortress.