Cut through the bedrock of the City of David during the reign of King Hezekiah around 701 BCE, this ancient water tunnel diverted the Gihon Spring into the Pool of Siloam inside Jerusalem's walls ahead of the Assyrian siege. The tunnel runs 533 metres in near-total darkness, and you can walk its full length wading through ankle-to-knee-deep water. Torches are available at the entrance; closed-toe shoes are essential.
The Siloam Tunnel is one of the oldest surviving examples of ancient engineering in the Near East. The original rock-cut inscription commemorating its completion was found carved into the tunnel wall in 1880 by a local boy — it is one of the earliest examples of Hebrew writing in existence and is now in the Istanbul Archaeological Museum. Entrance is from the City of David archaeological park, just outside the Old City walls near the Dung Gate.