This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

This castle-fortress is a living example of the transition from medieval defenses to modern fortifications.

Now a memorial, this factory was once used as a concentration camp for artists by the Vichy government.

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

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

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 1,400-year-old abbey was once a powerhouse for music and intellectualism known across Normandy.

A daring D-Day assault by U.S. Army Rangers is commemorated atop the high cliffs of this strategic point.

A small house sits between two huge rocks, with its back to the sea.

A massive, secret marina for the Nazis' most formidable weapon in the Atlantic.

These crumbling Nazi artillery bunkers are now fair game for massive graffiti projects.

This futuristic observatory at the top of the Pyrénées offers unrivaled views.

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

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.

A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

You must take the A train... to the last active cemetery in Manhattan.

This secluded ruin was once a home for exotic plants.

One of the oldest Jewish cemeteries in the city, it is now overgrown with an urban forest.

A once crucial portion of the Long Island railroad still lays abandoned, waiting to be turned into an urban park.

In its day this historic fort held 100 cannons pointed in almost every direction to protect New York.

This small, hidden cove is home to abandoned boats.