An unusual cave filled with rare alien-looking aragonite formations.

Also known as the Blue Church, the building was consecrated to the daughter of Andrew II.

The haunting concrete remains of a Nazi pebble crusher can still be found in this small French commune.

Old vessels have been transformed into artistic canvases in this unusual cemetery.

This army of concretions is an unexplained geological phenomenon unlike anything else in the world.

The largest crypt ever constructed in France was built in the 11th century on an ancient Druid sacred site.

Underneath a chalk hill in France lies what Hitler hoped would be the underground launching base for a devastating new weapon.

This otherworldly French waterfall looks like its waters have turned to stone.

Bits of architecture from a town destroyed in World War I now decorate this hotel garden.

This crumbling, graffiti-covered mansion sits tantalizingly within reach of the proletariat who frequent a public park.

An art world insider finds himself battling for his artistic home.

Trek into the depths of the cave where 17,000-year-old paintings exist alongside 400-year-old graffiti.

The Church of the Annunciation was carved into the face of a cliff, just like the rest of the town of Haute-Isle.

The post-apocalyptic remnants of a bucolic town ruined by a plane crash.

One of the largest ochre quarries in the world, hidden in a limestone landscape.

The remains of 40,000 humans, meticulously stacked in a tiny churchyard shed.

The deserted pirate-themed restaurant still entices explorers.

The 16th-century church was kept in its ruined state as a reminder of the casualties of World War I.

An enchanting work of outsider art, full of whimsical sculptures and carvings.

A self-built mosaic house and sculpture park.

Ghosts of France's colonial past.

A beautiful and classically designed villa, with an hourly infestation of monsters.

Beautiful carved tunnels.

A public park off the beaten path with a beautiful waterfall and 13th century Cistercian abbey.