Remains of a Roman arch in Trieste's old town
Originally an Illyrian settlement the town was later captured by the Carni. From 177 BC Tergeste was under the Romans. It was granted the status of colony under Julius Caesar, who recorded its name as Tergeste in his Commentarii de bello Gallico (51 BC). During Roman times, Tergeste was defined an "Illyrian city" by Artemidorus of Ephesus, a Greek geographer, and "Carnic" by Strabo.
In imperial times the border of "Roman Italia" moved from the Timavo river to Formione (today Risano). The Roman Tergeste lived a flourishing period due to its position as a crossroad from Aquileia, the main Roman city in the area, and Istria, and as a port as well, some ruins of which are still visible. Augustus built a line of walls around the city in 33-32 BC, while Trajan built a theatre in the 2nd century AD.
In the Early Christian era it remained a flourishing center, and after the end of the Western Roman Empire (in 476), Trieste was a Byzantine military outpost. In 567 AD the city was destroyed by the Lombards, in the course of their invasion of northern Italy. In 788 it became part of the Frankish kingdom, under the authority of their count-bishop. From 1081 the city came loosely under the Patriarchate of Aquileia, developing into a free commune by the end of the 12th century.
Trieste in the 17th century, in a contemporary image by the Carniolan historian Johann Weikhard von Valvasor
After two centuries of war against the nearby major power, the Republic of Venice (which occupied it briefly from 1369 to 1372), the main citizens of Trieste petitioned Leopold III of Habsburg, Duke of Austria to become part of his domains. The agreement of cessation was signed in October 1382, in St. Bartholomew's church in the village of Šiška (apud Sisciam), today one of the city quarters of Ljubljana. The citizens, however, maintained a certain degree of