Under the City of David at the south end of Jerusalem there is an amazing tunnel that connects Gihon Spring, a primary water source for ancient Jerusalem, to the Pool of Siloam. 

It’s name comes from the the time of King Hezekiah who, in protecting Jerusalem from the impending invasion of the Assyrians in the 8th century BCE, had the tunnel constructed to secure the city’s water supply.

Ancient engineers began at the two ends working toward the middle and, in a way not yet understood, meet within about a foot of each other deep underground.

The tunnel is narrow and claustrophobic yet bears witness to the prowess of the workers. I guess when a powerful empire is looming on the horizon there is a lot of motivation to accomplish important tasks.