The Tigris is the eastern member of the two great rivers that define Mesopotamia, the other being the Euphrates. In Greek, Mesopotamia means between two rivers. The river flows south from the mountains of southeastern Turkey through Iraq and empties itself into the Persian Gulf. The Ancient Greek form Tigris was borrowed from Old Persian Tigrā, itself from Elamite Tigra, itself from Sumerian Idigna. The original Sumerian Idigna or Idigina was probably from “running water”, which can be interpreted as “the swift river”, contrasted to its neighbor, the Euphrates. Another name for the Tigris used in Middle Persian was Arvand Rud, literally “swift river”. Today, however, Arvand Rud refers to the confluence of the Euphrates and Tigris rivers (known in Arabic as the Shatt al-Arab). In Kurdish and in southeastern Turkey the river is known as Dicle also known as Ava Mezin, “the Great Water”. Rising in the Taurus mountains of southern Turkey, the Tigris flows southeast through Iraq, where in the southern part of that country it merges with the Euphrates to become the Shatt al Arab, which then flows to the Persian Gulf. The river has numerous small tributaries running from its eastern bank, and is 1,180 miles (1,899 km) in length.
If you look around the Harran valley, you do not see any stones on the valley floor. The stone was quarried from the edges of the valley and transported to Harran. The length of the walls and the buildings required a lot of stone, again quarried at the edge of the valley 10-20 miles away. If you look closely at the walls surrounding Harran, you will notice that the majority of the wall is constructed of earthen works, with only a relatively short stone wall at the top. This speaks to the value and scarcity of stone. Large caves lie 11 miles (18 km) northeast of Harran on a road named for the Han-e Barür Caravanserai, and have gradually come into being over the centuries as stone was quarried for construction in the cities of Harran and Şuayb. The largest of the caves in places has two levels, and is made up of long galleries and tunnels.