Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

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

The ruins of an ancient stadium that hosted gripping chariot and horse races.

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

The final resting place of the great navigator, or maybe his brother.

Amsterdam's former hotspot for public executions and dissections.

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

The library's graceful rotunda is like a bibliophile's temple.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

It houses the remains of a 17th-century version of the Titanic.

Stockholm's deepest subway station is also a stunning ecological wonder.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

Copenhagen's celebrated theme park and gardens.

Old Danish castle immortalized in Shakespeare's Hamlet.

One of the world's largest tanks mimics the experience of watching rare whale sharks, giant rays, and deep sea creatures from the ocean floor.

Watch the newest land on the planet form before your eyes.

These picturesque Hawaiian falls are home to a rare species of fish that uses a special sucker to climb up cliffs.

Earth's tallest volcano is sacred to Native Hawaiians, and home to a dozen world-class observatories.

The air force base preserves its scars from the Japanese attack on Pearl Harbor.

An authentic replica of an Asian temple and garden hidden amongst the natural beauty of Hawai'i.