The medieval "Bearded Man" relief still serves as a clever flood warning marker.

The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

The palace window through which Protestant nobles flung two Catholic regents, thus sparking the Thirty Years' War.

Countless grotesque faces stare out from this eerie Prague art wall.

A significant example of Czech cubist architecture—a style you won't find anywhere else in the world.

This Prague museum collects brutalist relics and memories from the country's former Soviet rule.

Conspiracy theories and occult legends surround this mysterious natural rock formation.

An old asylum graveyard that's been abandoned for half a century attracts those seeking a dark thrill.

One of the oldest, well-preserved water treatment facilities in all of Europe.

Romania's "Red Ravine" is a little-known natural wonder that bears a resemblance to the Grand Canyon.

Nine centuries-old fortresses guard the walls of this medieval Romanian city.

This hauntingly beautiful cemetery outside a medieval citadel is full of winding paths and ivy-covered graves.

A medieval church built up to defend its village.

No one knows who built this strange cave of worship or exactly why.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

In a long-dry lake bed, these groups of massive stone pillars bear a striking resemblance to clumps of everyone's favorite fungi.

Thousands of rusting train cars have been slowly falling apart on the edge of Greece's second largest city.

A man's head is enshrined beneath a statue near the first building constructed for the modern Olympic Games.

Where commuters walk through remnants of an ancient Greek necropolis.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

These ruins of a sacred Ancient Greek temple stand next to a luxurious modern resort.

An important example of architectural history slowly decays in the city center.

Scars of this building's past life as a violent prison still cover its walls.

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.