Another much frequented caravan route was that which started at the mouth of the Narenta and passed through Bosnia and Servia. Ragusan goods were transported either wholly by sea round Sabbioncello or _via_ Stagno to the little island of Osinj in the river delta, where a trading depôt was opened. Close by were several other depôts, the most important of which was the _Forum Narenti_ (called Driva by the Slaves), with a large customs station, salt stores, and a Ragusan colony. Later it was supplanted by the Venetian castle of Gabela or Gabella.[228] The caravans travelled from the mouth of the Narenta through the land of Hlum, following the course of the river to Blagaj, the residence of the lords of Hlum (afterwards Dukes of St. Saba or the Herzegovina), above the spot where the river Buna springs full-grown from the rocks.[229] The route continued up the Narenta valley, as the railway does to-day, past Konjica, which was to play an important part in later times, over the Ivan Pass to Visoko in the centre of Bosnia, the castle of the Bani. Below was the town of Podvisoko (Sotto-Visochi in Ragusan documents), on the banks of the river Bosna. Between 1348 and 1430 this was the commercial capital of the country and the seat of important trading communities. From Visoko the route proceeded to Olovo and Borač, near Vlasenica,[230] where it branched off into three. One led eastward to Srebrnica, the centre of the silver-mining district,[231] and Rudnik; another went northwards to Soli; the main route went to Kučlat, well known as a trading station in the fourteenth century, with a large Ragusan colony, to Zvornik and across the Drina to Sirmia and Belgrad. At Sirmia,[232] which was on the ruins of the Roman Syrmium, the Ragusans had a flourishing settlement protected by the Kings of Hungary, until the town was burnt by the Turks in 1396. Its importance was due to its position as a starting point for the Ragusan traders going to all parts of Hungary.[233] These various routes were called collectively the _Via de Bossina_ in the Ragusan documents. The routes which started from the coast at points south of Ragusa were denominated the _Via de Zenta_.[234] Ragusan vessels sailed down the coast, and either discharged their goods at the towns of Antivari and Dulcigno, or sailed for some distance up the various rivers—the Bojana, the Drim, the Mat, the Išmi, the Vrego, the Devol, and the Vojussa. This stretch of coast, which had formed part of the Byzantine theme of Dyrrhachium, was under Servian rule from 1180 to 1440.