This Soviet-era "closed town" was a top secret uranium producer often left off of maps.

This former peat factory was transformed into an observatory before being abandoned once again.

These waste baskets play a few risque messages to discourage littering.

This Luxembourg cave is covered in cryptic looking marks left by mining activity.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

This tri-part waterfall is a little bit of fairytale beauty in the heart of Luxembourg's Little Switzerland.

Now overgrown, these anti-tank barriers from World War II are sometimes called "dragon's teeth."

This striking fort on the Maginot Line looks just as it did after being destroyed in the Fall of France.

Deep in the limestone cliffs of the Alabaster Coast, a German fortress built during World War II.

Science fiction's grandfather has a fittingly marvelous tomb.

A centuries-old complex of hand-dug stone chambers has sheltered locals in times of trouble.

Each spring, a dreamlike carpet of bluebells overtakes the forest floor.

A magical and peaceful ruined Cistercian abbey in what is now southern Belgium.

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

These ruins reveal the remarkably intact layout of a Roman marketplace.

An underground city of ancient quarry tunnels hid thousands of Allied soldiers in WWI.

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

A collection of weird and wonderful art fills a former houseplant nursery.

One of Belgium's oldest hospitals saw patients from the 13th to 20th centuries before becoming a museum.

This bunker in northern France was built by Nazi German forces with the intention of launching up to 50 V2 rockets at London each day.

The tomb of a hard traveling saint is constantly covered in shoes as offerings to heal disabled youth.

These rustic holiday homes are made from discarded fishing boat hulls.

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

A set of 27 bamboo tubes creates an eerie soundscape that changes with the wind.