IT'S CALLED MIQUEAS IN ARABIC.
IT USED TO HELP MEASURING THE WATER LEVEL DURING FLOOD (AUGUST-SEPTEMBER)IN ORDER TO REGULATE THE DISTRIBUTION OF WATER FOR IRREGATION AND AMOUNT OF TAXES PAID.
THE ONE LOCATED AT RODAH ISLAND IS THE 10TH OF ITS KIND TO BE BUILT .IN ISLAMIC PERIOD,NON OF THE EARLIER ONES SURVIIVED.
IT'S SO CLOSE TO THE COPTIC CAIRO AREA YOU CAN REACH BY THE METRO OR TAXI.