This sturdy, circular stronghold served as one of the forts that protected the Venetian Lagoon.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

The courtyard of this small Marinid madrasa is a dazzling example of intricate Islamic architecture.

An awe-inspiring mosque in Morocco with one of the tallest minarets in the world.

Morocco's largest Jewish cemetery.

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

This vast masterpiece of Moroccan architecture spreads across 20 acres.

The largest cactus farm in Africa.

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.

It took 40 years to build this Eden-like garden in Marrakech, later restored by Yves Saint-Laurent.

Along the most northwestern point in Africa is an ancient cave surrounded by legends.

Also known as the Square Colosseum, this building is a prime example of fascist-era rationalist architecture.

A forgotten "city of water" underneath the famous Trevi district.

This ancient trail climbs the mountain where a Latin League cult worshipped Jupiter, its main deity.

After this one-of-a-kind palace was built the architect's hands are said to have been cut off to keep it that way.

Burial site of a Jewish prophet revered in Iran.

Slovenia's first mosque is a striking mix of Islamic and modernist architecture.

A relic from the Industrial Revolution got a second life as a contemporary performing arts space.

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

A trough of 700 strange bronze faces runs through a narrow alley in Ljubljana's old town.

This abandoned Slovenian military barracks has become a punky-political art squat.

A miniature train-ride through Slovenia's largest cave system.

This region of Slovakia boasts some of the most plentiful opal mines in the world.