The production of soap is a very old tradition in the region of the Middle East called Bilad al-Sham (the name given to the geographic unit of Syria, Lebanon, Jordan and historical Palestine, which was before World War I a subset of the Ottoman Empire. This is a sub-set in a representational way as the Bilad al-Sham was never an administrative Ottoman district). This tradition is based primarily on the growth of olive trees. Whether on the coast or in the hinterland, the centers of soap are all former olives press centers. Soap is primarily a domestic production of the villages, where they used the remains of the oil production. Gradually urban centers of production developed "soap cities." The most famous are Aleppo in Syria, Tripoli in Lebanon and Nablus in Palestine.