Trebinje (, ) is a city and municipality located in the Republika Srpska entity of Bosnia and Herzegovina. It is the southernmost city in Bosnia and Herzegovina and is situated on the banks of Trebišnjica river in the region of East Herzegovina. As of 2013, it has a population of 31,433 inhabitants. The city's old town quarter dates to the 18th-century Ottoman period, and includes the Arslanagić Bridge, also known as Perovića Bridge. Geography Physical geography The city lies in the Trebišnjica river valley, at the foot of Leotar, in southeastern Herzegovina, some by road from Dubrovnik, Croatia, on the Adriatic coast. There are several mills along the river, as well as several bridges, including three in the city of Trebinje itself, as well as a historic Ottoman Arslanagić Bridge nearby. The river is heavily exploited for hydro-electric energy. After it passes through the Popovo Polje area southwest of the city, the river – which always floods in the winter – naturally runs underground to the Adriatic, near Dubrovnik. Trebinje is known as "the city of the sun and platan trees", and it is said to be one of the most beautiful cities in Bosnia and Herzegovina. The city is the economic and cultural center of the region of East Herzegovina. Political geography The Trebinje municipality is located in the most southern part of Republika Srpska and the municipalities of Bileća, Ljubinje and Ravno in Herzegovina-Neretva Canton of the Federation of Bosnia and Herzegovina. The Trebinje municipality has an area of 904 km2 and makes up 3,68% of the total territory of the Republic of Srpska. Climate Trebinje experiences a Humid subtropical climate (Cfa) with heavy precipitation, typical of the southern Adriatic coastal areas. History Middle Ages De Administrando Imperio by Constantine VII (913–959) mentioned Travunija (Τερβουνια). Serbian Prince Vlastimir (r. 830–51) married his daughter to Krajina, the son of Beloje, and that family became hereditary rulers of Travunija. By 1040 Stefan Vojislav's state stretched in the coastal region from Ston in the north, down to his capital, Skadar, set up along the southern banks of the Skadar Lake, with other courts set up in Trebinje, Kotor and Bar. The town commanded the road from Ragusa to Constantinople, which was traversed in 1096 by Raymond IV of Toulouse and his crusaders. Trebinje diocese has its episcopal seat in Polje near Trebinje. At the end of the 12th century Stefan Nemanja