The final resting place for the remains of 143 Habsburg royalty.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

A mountain pass in Bulgaria's Balkan Mountains was the site of four historic battles.

This ancient theater, restored in the 20th century, lives on as a venue for dramatic and musical performances.

An abandoned saucer-shaped monument in the Bulgarian mountains.

Over 100 towers were built in Bologna during the Middle Ages, but only 22 survive.

This zoological museum began as the first great curiosity cabinet.

Thousand-year-old Viking runes adorn an ancient Greek lion at the entrance to the Venetian Arsenal.

Hanging within this medieval church are the bones of a beast allegedly slain by a fourth-century saint.

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

One of Mother Nature’s geological gems, home to many prehistoric fossils.

Louise Bourgeois' 30-foot-tall steel spider sculpture.

The entire length of the border is marked by a 20-foot-wide slash through the trees.

Canada's subterranean Cold War museum has doubled as a movie set.

A grand Gothic Revival basilica with stained glass depictions of Montreal's religious history has only one soul resting in its crypt.

A 98-room castle in the middle of Toronto that bankrupted a 19th century electricity multimillionaire.

These caves secretly held national treasures during World War II.

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.

Romania's triumphal arch looks out over Bucharest.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

This once-derelict building is now one of the most beautiful bookstores in the world.

17th century palace once a meeting place for politicians.