The most revered place in Chittagong is the Dargah or shrine of Hazrat Bayazid Bostami, a celebrated saint born in Bostam , Iran in 777 AD. It is a popular belief that he visited Chittagong. Emperor Aurangzeb built a mosque on the bank of a big tank at the foot of the hillock on which the shrine stands. The tank contains several hundred tortoises and it is traditionally believed that the tortoises are the descendants of the evil spirits whose ancestors, having incurred the wrath of the great saint, were metamorphosed into tortoises.