The city lies in the Trebišnjica river valley, at the foot of Leotar, in southeastern Herzegovina, some 30 km (19 mi) 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.