Tigris tunnel

The so-called Tigris tunnel is a cave approximately 50 miles north of Diyarbakır in Turkey. It has a length of about 750 m (2,461 ft). The Berkilin Cay flows through this cave. It forms a source of the Tigris, but not the main one, although the exit was long believed to be this. In fact, the spring is near Bingöl not far away from the Tigris tunnel. In its vicinity there are several archaeological monuments, three Assyrian Empire and Neo-Assyrian rock reliefs and five inscriptions.