All that remains today of the magnificent bridge across the Tigris (Dicle) at Hasankeyf are two massive stone piers in the river and one arch of the northern approach. According to Ibn Havkal the bridge was built in 1116 by Fahreddin Karaaslan.
The northern approach has an extra arch (still standing), as it starts low on the flood plain and must reach the same level as the southern approach where it begins on the cliff above the river. It also had some rooms on each side of the road, which may have been for toll collecting or for housing travelers. The roadway was carried across the central span of the bridge on a timber arch and through towers atop the supporting piers. The timber arch allowed it to be removed in times of siege, thus rendering the city inaccessible. The piers were carved with figural relief, now badly worn, but thought to have been signs of the zodiac.
Sources:
Sinclair, T. A. Eastern Turkey: an architectural and archaeological survey. London: Pindar Press, 1989.
Zengin, Burhan. Hasankeyf tarihi ve tarihi eserleri. Ankara: n.p., 1994.