The Nilometer in Modern Cairo on the southern tip of Rawda (Roda) Island facing al-Fustat to the east is a rather unique historical site often overlooked by visitors to Cairo. It has the properties of being one of the oldest structures in Cairo built after the Arab conquest, as well as having a link to Egypt's pharaonic past. This Nilometers, in Arabic known as a miqyas (Mikyas al-Nil), was used to measure the flood levels of the Nile River and is a heritage of Egypt's distant past, when such structures doted the course of Egypt's grand river. These types of devices continued to be useful up until the modern era when the Nile was tamed by modern dams. During August and September, it was used to regulate the distribution of water as well as to compute the levy of taxes paid as tribute by Egypt to the the Arab Caliph, since the generosity of the Nile was in large part an indication of Egypt's prosperity.