Sometimes it is necessary to bury the past. However, it is even better to bring it back to light now and then. In the early 1980s, Aga Khan IV, a descendant of the Fatimid Caliphs and among the world's wealthiest royals, decided to endow Cairo with an oasis. He chose an abandoned piece of land full of garbage and ruins. It cost 30 million US dollars, and the massive movement of soil and rubble (80,000 truckloads) to create the gardens of Al-Azhar. Historical Islamic gardens influence the design with formal terraced gardens, numerous fountains and waterways, multicoloured stonework (a homage to the Mamluks), and the quintessential Islamic geometry. However, the greatest surprise was discovering a 1.5 kilometres (almost 5000 feet) section of the Ayyubid fortifications (complete with towers and curtain wall) buried beneath the wreckage along the park's western side.