Devious political maneuvering and four ancient, working telescopes are central to the world's second-oldest observatory.

A former plague hospital turned medical museum.

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

The prototype for all Nazi concentration camps.

Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

One of downtown Berlin's last reminders of its Communist past.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The most visited, and possibly most controversial, museum in Germany.

The fairy tale castle of the “fairy-tale king,” this was also the inspiration for Disney’s “Sleeping Beauty.”

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

"Portugal's Stonehenge" is made up of nut-like stones aligned with the heavens.

Don't miss the xylotheque (a library of wood) at this museum devoted to cork.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

One man's remarkable private collection of art from around the world.

This unique architectural wonder is also tied to one of the 20th-century's most renowned writers.

After the owner of this Art Nouveau home died, it was turned into a museum displaying a lifetime dedicated to art.

A museum dedicated to one of Portugal's most celebrated writers.

The Roman city was the birthplace of various emperors and is home to one of the empire's most impressive architectural feats.

Spain's largest bullring offers a unique glimpse at architecture and history.

A 16th-century Andalusian palace.

Its appearance in "Game of Thrones" may spur on the long-awaited restoration of this medieval shipyard.

The world's largest wooden structure.