6Abram believed the LORD, and he credited it to him as righteousness. 7He also said to him, "I am the LORD, who brought you out of Ur of the Chaldeans to give you this land to take possession of it." 8But Abram said, "O Sovereign LORD, how can I know that I will gain possession of it?" -Genesis 15:6-8
The site is marked by the ruins of a ziggurat (right), still largely intact, and by a settlement mound. The ziggurat is a temple of Nanna, the moon deity in Sumerian mythology.
It has has two stages constructed from brick: in the lower stage the bricks are joined together with bitumen, in the upper stage they are joined with mortar. Ur at its height had around 30,000 residents.