Sliven (slēˈvĕn) [key], city (1993 pop. 106,958), E central Bulgaria, at the foot of the Balkan Mts. A textile center, it also produces carpets, wood and metal products, foodstuffs, and wine. Sliven is the seat of an Eastern Orthodox metropolitan. The city has long been strategically important because of its location at the entrance to Balkan passes. There are several churches and mosques and the ruins of a medieval fortress. Sliven is also known as Slivno.