The fortifications lie in uninhabited or very sparsely inhabited territory. They consist of
sand and
stone walls or
berms about in height, with bunkers,
fences, and
landmines throughout. The barrier minebelt that runs along the structure is thought to be the longest continuous minefield in the world. Military bases, artillery posts and airfields dot the Moroccan-occupied side of the wall at regular intervals, and
radar masts and other electronic surveillance equipment scan the areas in front of it. The following is one observer's description of the berm from 2001: In all, six lines of berms have been constructed. The main ("external") line of fortifications extends for about . It runs east from
Guerguerat on the coast in the extreme south of Western Sahara near the Mauritanian town of
Nouadhibou, closely parallelling the
Mauritanian border for about , before turning north beyond
Tichla. It then runs generally northeastward, leaving
Guelta Zemmur and
Smara, again crossing Mauritanian territory and reaching
Haouza in Moroccan-held territory, before turning east and again closely following the
Algerian
border as it approaches Morocco. A section extends about into southeastern Morocco. Significant lines of fortifications also lie deep within the Moroccan-occupied area. Their exact number and location have been ignored and not well understood until 2004 by international commentators. All major settlements in Western Sahara, the capital
Laayoune, and the
phosphate mine at
Bou Craa lie far into the Moroccan-held side. ==History==