Gadara Aqueduct, Roman aqueduct tunnel system between Dille, Syria and Umm Qais, Jordan.

The Gadara Aqueduct, also called Qanatir Fir'awn, was a Roman water system about 155 km long that supplied Adraha, Abila and Gadara. It began near Dilli in southern Syria at a Roman dam and ran above ground at first, crossing wadis on bridges five to ten metres high. In what is now Jordan the line continued as a tunnel of 106 km, built through roughly 2,900 vertical and diagonal shafts up to 70 m deep, with cut marks still visible on the rock walls.

The system was probably begun in the 1st century AD and largely finished in the 2nd, serving Adraha, Abila and Gadara for over 400 years, with parts in use until the 12th century. A 25 km stretch failed because of surveying or construction errors, so the 30 km Turab aqueduct, built in the 1st century BC, was folded in to carry water to Gadara. Mathias Döring of Hochschule Darmstadt researched it from 2004.

Local tradition calls the channel Qanatir Fir'awn, "Pharaoh's Watercourse", and the Arabic name Qanat Fir'aun is still used for it. Nineteenth-century travellers Johann Gottfried Wetzstein (1860) and Gottlieb Schumacher (1896) reported an underground city beneath Adraha whose inhabitants drew water from the channel with jars on ropes; no trace of it survives, and modern scholars read their accounts as misinterpreted excavation features.

The tunnel runs at a gradient of about 0.3 metres per mile, so water moved by gravity alone. It was built through roughly 2,900 vertical and diagonal shafts up to 70 m deep, many with stairs down to the channel. The first European to ride along the line was Ulrich Jasper Seetzen in 1805; much of the route lies in open terrain near Dilli and Dera'a.

Nearly all of the roughly 2,900 construction shafts along the tunnel were cut at a diagonal of 45 to 60 degrees, with stairs leading down to the water channel inside the mountain. The first Western traveller to ride along the line, called Kanatir, was Ulrich Jasper Seetzen in 1805.