Hezekiah's Tunnel

When Sennacherib marched on Judah, Hezekiah stopped the springs outside the city and drove a tunnel through solid rock from the Gihon Spring to the Pool of Siloam. Two teams cut from opposite ends and met in the middle — a feat recorded on the Siloam Inscription, one of the oldest Hebrew inscriptions ever found.

Walking it today is the closest thing in Jerusalem to time travel: knee-deep water, chisel marks still sharp on the walls, and the sudden widening where the two crews finally heard each other through the stone.