An ancient tunnel in Jerusalem built to redirect water in the event of a siege is one of history’s great architectural innovations.

The maze-like transportation hub contains abandoned areas, derelict stores, and a resident bat colony.

A serene desert oasis speckled with ancient artifacts.

This subterranean funicular is one of the world's smallest subways.

As the Dead Sea continues to deplete, massive sinkholes open along its banks.

A massive, heart-shaped, wind-carved crater in the middle of the Israeli desert.

Squeezing inside this deep, narrow canyon reveals a festival of desert colors.

An ancient quarry rediscovered by a dog and claimed by biblical kings, a German cult, and the Freemasons.

The home of the Dead Sea Scrolls is an abstract modernist dream.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

Descend 2,030 years into the past in an ancient tunnel built to support Jerusalem's most famous wall.

These numerous Israeli caves were dug out over hundreds years for reasons ranging from hideouts to burial sites.

You can row a boat through this ancient underground reservoir.

A Victorian Gothic masterpiece housing a world-class collection of rare books and manuscripts.

A network of concealed passageways lies within a busy London Underground station.

Romania's "Red Ravine" is a little-known natural wonder that bears a resemblance to the Grand Canyon.

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

A subterranean shelter remains intact under a busy Paris railway station.

This massive library holds what was once the largest book collection in the world.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This fortress was designed to prevent a Nazi invasion but was never used.

The beautiful baroque library of the Hapsburg empire.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

Dine amidst exotic plants at this former royal greenhouse.