The world's oldest bookshop still in operation.

Eat the ultimate iteration of Portugal's most beloved pastry.

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

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

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

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.

Kissing the ass of this stone lioness has become a rite of passage in the city of Girona.

This stunning iron gate designed by Modernist architect Antoni Gaudí is filled with mythic symbolism.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

The site of a concentration camp where inmates were made to take part in one of the largest counterfeiting operations in history is now hauntingly empty.

Germany's Glienicke Bridge has a shady history of clandestine meetings, espionage, and spycraft.

The "Prussian Versailles" that is as glorious today as when it was built.

If you visit the burial place of King Frederick the Great, you'll likely find a couple of potatoes sitting on his tombstone.

Cold war icon and onetime "hole" in the iron curtain.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

A memorial in the Tiergarten is a reminder of the suffering inflicted on homosexuals by the Nazi regime.

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

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

The site where a plot to assassinate Hitler was planned—and its conspirators were executed—is now a powerful memorial to the German resistance during World War II.

After a nearly successful attempt on Hitler's life, the conspirators met their fate in the courtyard of this Berlin building.

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

This historic black and white monastery is one of Bulgaria's architectural jewels.