One of the most valuable palace-garden complexes in the eastern borderlands—and one of the most haunted.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

Living fossils in this remote Australian bay provide a glimpse of what Earth may have looked like 3.5 billion years ago.

The development of this cliffside waterpark is representative of Mexico's history of co-op tourism developments.

These paved rills bring freshwater into Altstadt and could spell wedding bells for whoever stumbles into the waters.

The first geometric self-supporting spiral stairs in Britain are a truly beautiful sight.

During the holidays, a vintage subway train whisks New Yorkers back in time.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

Blue-green pools and smooth stones comprise one of Spain’s most idyllic hidden wonders.

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

These magnificent city walls rise from the barren sun-baked Spanish plains like something straight out of a fairytale.

The first tunnel to be dug beneath a river, repurposed as an art and museum space.

Elevated freight railway turned wildly successful urban park.

Apartment complexes built into huge repurposed natural gas tanks.

Volcanic rocks ground down into sand make this Spanish beach as black as night.

A boardwalk winds through this sliver of coastal nature hidden within Sydney.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

A market built atop boats is one of the few floating holiday markets in Europe.

A creepy statue of a hooded ghost hauls itself up from the water in a historic Lithuanian city.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

A unique collection of diving equipment spanning antiquity to the present day.

Known as the Sistine Chapel of Egypt, this tomb houses some of the most well-preserved paintings in Egypt.

Rare recess caves fill this unbelievably beautiful Ohio park.