An unfinished tomb carved into a giant boulder in the Arabian Desert.

At the right time of day, sunlight floods through the roof of this cave and illuminates the small pavilion hidden within.

This popular cave pool is truly magical, despite the crowds.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

The most remote tree in the world is more than 170 miles from its nearest neighbor.

A memorial to a goat culled during a foot and mouth disease outbreak guards a series of fantastical caves.

This remote island in Iowa was abandoned after being devastated by flood.

The abandoned zoo enclosures offer a perfect place to experience the other side of the bars.

These otherworldly caverns form Earth's oldest known cave system.

The ruins of a pre-Columbian fortress city so secure it held off the Spanish conquistadors for over 20 years.

Hiding behind a grocery store is a spectacular cavern carved as part of an old limestone quarry.

Tens of thousands of ancient rock carvings hidden in the heart of a French national park.

The ruins of an ancient pyramid built by the mysterious Chupícuaro civilization.

The words of the neighborhood's most famous poets adorn four concrete walls.

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

The verdant mossy ruins of a Franciscan monastery lie in the remote Sintra hills awaiting exploration.

On this wooded path, a stained-glass window creates a spellbinding forest cathedral.

On this stunning Scottish island, you can walk in the footsteps of dinosaurs.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

Strange rock formations tower above the river that snakes through this enchanting Icelandic canyon.

Rare recess caves fill this unbelievably beautiful Ohio park.

The land is full of geologic eye candy, such as otherworldly spires, mushroom-shaped hoodoos, and prehistoric fossils.

This isolated island is often capped by its own fluffy cloud.

Fourteen curious and controversial white bunnies sit in a circle near Newport Beach City Hall.