Trebinje (Serbian Cyrillic: Требиње) is the southernmost municipality and city in Bosnia and Herzegovina. Located in East Herzegovina, it is part of the Republika Srpska entity, and its population numbers 31,433 (2013). The Trebišnjica river flows through the heart of the city. The city's old town quarter dates to the 18th-century Ottoman period, and includes the Arslanagić Bridge.