This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

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.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

This remarkable checkered church on a Corsican hilltop is fabled to have been built by angels.

This church sits upon a peaceful hill and a long, turbulent history.

Personal garden filled with mosaics made of recycled garbage.

Resting on a hill overlooking the coast, these medieval ruins look completely deserted save for their restored chapel.

A castle-like sea fort from the 17th century is now a museum to oyster farming.

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

The man who introduced reinforced concrete to the world demonstrated its genius by using it to build his own house.

Fighting the British and making game shows for over 150 years.

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.

An icy lake tucked among jaw-dropping alpine panoramas.

Despite centuries of architectural innovation, this French castle is being built like it's the 13th century.

A chapel on a volcanic core, marking the end of a successful journey.

Beautiful carved tunnels.

These quaint French houses dangle precariously over a precipice.

The fantastic architectural models of a French traveler.

The largest underground church in Europe.

Do these monsters look familiar? The gargoyles on this church are all from pop culture.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

Egyptian Revival movie palace abandoned for decades and restored in 2013.