This beautiful system of tunnels built into natural rock serves as a centuries old plumbing system.

Mirrors and glass shards cover every inch of this arrestingly beautiful mosque.

Putrefaction plateaus in Iran, where the dead were sent for decontamination before going to their final resting place.

Julia Morgan's Moorish-Gothic labyrinth of fountains, trees, natural light and Oakland's notable dead.

Once thought to be the oldest living tree in the world, Methuselah was germinated before the Egyptian pyramids were built.

Tiki luxury on Nob Hill.

Quite simply the largest tree in the world (by volume).

Towering basalt columns, a creation of fire and ice.

This awesome Spanish castle is so fantastical it was actually used on Game of Thrones.

Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

A Lycian city of the dead carved into the hillside of Southern Turkey, complete with startlingly human touches.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

Moorish signal station on a stratgic rocky outcrop.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

Unique geological formations in China, featuring some suggestive shapes.

270 million year-old forest of stone.

The most famous location in China was home to whole dynasties worth of imperial rulers.

One of the most well-preserved temples of ancient Egypt.

A 140-year-old castle with underground caves hidden in San Francisco.

This stone complex marks the urban center of a lost civilization.