Though it is relatively small in size, Tunisia has great environmental diversity due to its north-south extent. Its east-west extent is limited. Differences in Tunisia, like the rest of the Maghreb, are largely north-south environmental differences defined by sharply decreasing rainfall southward from any point. The Dorsal, the eastern extension of the Atlas Mountains, runs across Tunisia in a northeasterly direction from the Algerian border in the west to the Cape Bon peninsula in the east. North of the Dorsal is the Tell, a region characterized by low, rolling hills and plains, again an extension of mountains to the west in Algeria. In the Khroumerie, the northwestern corner of the Tunisian Tell, elevations reach 1,050 metres (3,440 ft) and snow occurs in winter.
The Sahel, a broadening coastal plain along Tunisia's eastern Mediterranean coast, is among the world's premier areas of olive cultivation. Inland from the Sahel, between the Dorsal and a range of hills south of Gafsa, are the Steppes. Much of the southern region is semi-arid and desert.
Tunisia has a coastline 1,148 kilometres (713 mi) long. In maritime terms, the country claims a contiguous zone of 24 nautical miles (44.4 km; 27.6 mi), and a territorial sea of 12 nautical miles (22.2 km; 13.8 mi).