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This circular tower is dated by its excavator, Kathleen Kenyon, to approximately 8,000 B.C. There actually is an interior staircase that exits by the iron grid that is on the top of the tower. The tower is located in the "west trench" that was excavated by Kenyon.
The tower is 28 ft. [8.5 m.] in diameter and is 25 ft. [7.7 m.] high!
Image from the Zondervan Atlas of the Bible, p. 89.