Believed to date from the 1st century, Aden Tanks were designed not just to collect precious water for the city, but also to remove water in times of flash flooding. A series of ingenious steps, arches and conduits channels the rainwater into a set of beautifully built cisterns. The 13 cisterns (all that remain of the original 53 tanks) have a total capacity of 20 million gallons. Developed by successive dynasties, the tanks eventually fell into disuse, until uncovered in the mid-19th century by the British, who, despite their best efforts and modern technology, never did manage to get them to work again.
