A monument to the three wars that led to German unification towers within a Berlin traffic circle.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

This "mathematical tower" was an observatory, early skyscraper, and place to reflect on all of nature and the cosmos.

The site of Austria's biggest concentration camp now honors its victims.

Archduke Ferdinand II's collection of rare objects is considered one of the oldest museums in the world.

Resting in the middle of an Austrian river, this sci-fi "island" lets people cross in neon style.

The shell of a medieval fortress offers commanding views of the area it once protected.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

The Habsburgs' royal collections of art and wonders.

A whimsical bridge adorned with decorative dragons.

This one-time health resort was used by aristocrats around the world.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

Venice's island of the dead.

Jesus' footprints and the first catacombs in the world.

This no man's land slicing through the island is strewn with abandoned relics of another time.

An image of the legendary saint stands in the shadow of a cathedral she liberated.

What looks like a normal building is really a hollow facade hiding a subway vent.

This medieval tower is all that remains of the castle where Joan of Arc was held before being burned at the stake.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

Notorious artist squat renovated into legal studios.