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

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

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

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

Two geological phenomena in one precarious locale: a towering stone window, and a deep blue void.

A centuries-old forgotten underworld lies beneath Malta.

The fishing boats that moor in this small lagoon enter and leave through a tunnel to the sea.

This prison on the Maltese island of Gozo is almost 500 years old, and they have the graffiti to prove it.

Stone Age solar temple is aligned with the sun on each equinox and solstice.

This local emblem is the oldest and largest dragon tree in the Canary Islands.

This unique rock formation is quite the local celebrity, although one day it may come crashing down.

According to the Guanches, the aboriginal people of the Canary Islands, the king of evil lives inside this volcano.

Lava stone structures possibly dating back to the 19th century may have been a stopping point for voyagers between ancient Egypt and the Mayan Civilization.

The farthest northwesterly point of the British mainland is one of the most remote places in the Scottish Highlands.

This staircase in a lush tropical grotto was built by enslaved laborers and renamed to honor Queen Victoria's role in ending slavery in the British Empire.

A lush oasis full of vibrant plants and striking geometric displays.

Inside this museum, the history of the Walt Disney Family empire is on full display.

Once the largest windmill outside of Holland, with enormous 114 foot sails.

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

Guns that have been defending San Francisco since 1904.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

The giant pair of sexy legs sticking out the window of this costume store have become its main draw.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

San Francisco's oldest surviving monument and meeting place for 1906 survivors.