Ghadamis is a city in Libya. It is a tranquil old city, with white, covered streets that are both dark and refreshingly cool. Ghadamis was built painstakingly based on a complex knowledge of how to deal with extreme temperatures. The positioning of Ghadamis' buildings is far from casual. Every angle, every wall, every opening in the roofs over the alleyways, are parts of the same organism. Ghadamis still stands, but the people have moved into the modern settlement nearby. Yet they still take refuge in the old city when summer becomes unbearably hot. With the exodus of its local population, and their resulting loss of knowledge of engineering buildings to maintain natural air conditioning, an important science could be lost. In its earlier days, the life line of Ghadamis was trans-Sahara trade, including the slave trade.