Nikola Tesla's ashes are held in a golden sphere, surrounded by his works.

The sophisticated hydraulic system of the Nazca civilization.

Conspiracy theories and occult legends surround this mysterious natural rock formation.

An ingenious solution to a tricky engineering problem, this spiraling bridge takes drivers for a dizzying spin.

Climb to the top of this spiritual tower, and you'll be rewarded with spectacular views.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

This enormous spiral sculpture looks strangely out of place on the edge of a housing development.

An architectural oddity of six stories, accessed by graceful ramps.

Built to test magnetically levitated elevators, the tower also boasts Germany's highest visitor platform.

The United States's largest hand-dug well is topped with a state-of-the-art museum.

A serene temple with stunning stained glass hides in downtown Dallas.

This high-design church is made up of two dizzying spirals meant to evoke the weaving together of marriage.

Featuring the largest CinemaScope screen in Pennsylvania, this drive-in has entertained moviegoers for more than half a century.

Brush shoulders with animatronic Arab leaders made of silicone.

Beirut's thinnest building was the result of feuding brothers.

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

6000-year-old coal fire moves one meter per year.

A natural gas leak provides a flickering flame beneath a waterfall.

Mysterious hillside with a continuously burning natural fire.

A fiery crater has been burning in the Karakum Desert since 1971.

An 18th-century Catholic church converted into an eccentric temple of music and bacchanalia.

You can row a boat through this ancient underground reservoir.

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

A maze of underground tunnels beneath one of the most beautiful forts in Serbia.