Hundreds of hidden passageways weave through the old quarters of Lyon.

Keshwa chaca, among the last handwoven Incan bridges, crosses Apurimac Canyon in Peru.

Bolivia's needle-like rock formations.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

An Aztec temple, the largest man-made pyramid in the world, sits buried in earth with a Spanish church set on top.

These Nubian pyramids are strange and unique, even by pyramid standards.

An Ethiopian "Jerusalem" featuring a church hewn out of a single rock.

This former insane asylum now holds a pathological anatomy museum.

A pyramid in Central Europe of unknown origin.

The gloomy ruins that inspired Bram Stoker to bring Dracula to life.

Once thought to be the mysterious work of a witchy prophetess, a well with unusual properties turns objects into "stone".

Bohemian paradise covered in majestic forests.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

Museum dedicated to the terror regimes of Hungary.

Once the home of a hermetic monk, this cave now houses a small church.

Limestone caves in the Cambodian countryside, once the site of genocide, now a place of peaceful beauty.

Every equinox this Maya pyramid puts on a spooky ancient light show.

This derelict superstructure was a very important warning system for the Soviet military.

This attraction was abandoned after the Chernobyl disaster.

The largest collection of death masks in Ukraine.

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

Ruins of a German Castle on top of a towering stone pillar.

A battle between nature and architecture in the Cambodian jungle.