Monastir, also called Mestir, is a city on the central coast of Tunisia, in the Sahel area, some 20 kilometres south of Sousse and 162 kilometres …Monastir, also called Mestir, is a city on the central coast of Tunisia, in the Sahel area, some 20 kilometres south of Sousse and 162 kilometres south of Tunis. Traditionally a fishing port, Monastir is now a major tourist resort. Its population is about 93,306. It is the capital of Monastir Governorate.