Double spiral staircases are not unheard of, but they are very rare.

One of the two original gateways into the Kasbah, this gateway is a nesting site for storks.

Numerous impressive carvings are embedded in the trees lining this street in Marrakech.

This vast masterpiece of Moroccan architecture spreads across 20 acres.

The oldest monument in Marrakesh and the city's only surviving example of Almoravid architecture.

Deliberately hidden for centuries, the magnificent Saadian Tombs were eventually uncovered in 1917.

The largest madrasa in Morocco once housed more than 900 students within its exquisite walls.

Fortune tellers, snake charmers, poets, and storytellers all gather on this historic square in Morocco.

Portugal's National Pantheon has a history of curses, collapses and financial problems.

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.

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

This once-forgotten oasis in the middle of Lisbon was first created over a century ago quite by accident.

Tucked away inside this concrete building is a church and its grand display of brutalist architecture.

At this concrete bunker on the Trondheim fjord, secrets lie above and below the water's surface.

The world's first and only escalator for lazy bicycles and their daunted riders.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

This column celebrates Rome's victory over the Goths, and may be the oldest Roman monument in Istanbul.

This half-forgotten fortress was constructed by the Ottoman conqueror of Constantinople.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

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

A marvel of Byzantine engineering under the streets of Istanbul.

You can spot this teeny tiny stained-glass window from the Bonifacius bridge.

Potato-peeling mannequins, Inca art, and a dangling tuber mobile help trace the history of fries at this Belgian museum.