The gorge has been widened by the flow of wafer. While today there is only water here during flash floods, it is likely that once a stream flowed through Wadi Mudhlim, providing water to the Nymphaeum in the city center to supplement water arriving there from the canalization system through the Siq. Wadi Mudhlim was altered in the first century BC by the construction of a massive tunnel that channeled the flash floods of ancient times away from the Siq, which was the formal entrance to the city. In Wadi Mudhlim is Sadd AL Ma'jin, a natural rotunda that is carved with many votive niches as seen in the insets. Water from the Wadi Mudhlim flowed through the Wadi Mataha, passing below the Tomb of Sextius Florentinus, and rejoined Wadi Musa at the Nymphaeum in the city center.