The central highlands of Yemen reach even more than 2000 meters of altitude. Here the soil is mainly of volcanic origin and the climate is dry but with a months-long rainy season. The combination of these elements makes the perfect ground for agriculture. Since the ancient times the highlands farmers terraced hillsides and prospered with crops of barley, wheat and sorghum. People still practice terrace farming in Yemen, but the oldest agricultural terraces, which have fallen into disrepair, probably date to 3000 B.C., making them among the oldest in the world.