Israel's most claustrophobic hiking trail, Hezekiah's Tunnel is an ancient narrow path below the City of David in Jerusalem. Built in 701 BC, the tunnel was constructed as an aqueduct to bring water to Jerusalem residents while the city was under siege by the Assyrians.

Today, visitors can hike through the S-shaped tunnel, also called Warren's Shaft, after explorer Charles Warren, who discovered the tunnel in 1867.

Crouching below the stone ceiling while wading through the water in the complete dark, it's hard to imagine how the 1,750-foot tunnel was even completed 2,700 years ago, let alone used as a functioning aqueduct. You can bring a flashlight, but it's more fun to use your hands as a guide and do it in the dark.