Climbing this abandoned railway leads to breathtaking vistas of O‘ahu.

The world's tallest circular building is loaded with symbolism, but many just see a big donut.

This Scottish castle has witnessed clan rivalries, Jacobite uprisings, whisky smuggling, and more.

A mesmerizing wonderland of salt-encrusted tree branches and pencil roots.

The cluster of igloo-like domes forms the remains of an ancient burial ground.

Over 3 miles up in the Himalayas this pass is one of the highest drivable roads in the world.

Its history includes dinosaur fossils, cattle rustlers, Georgia O'Keeffe, and a mythical giant rattlesnake named Vivaron.

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.

This ancient tunnel is one of the most important examples of Roman hydraulic engineering in Spain.

This retro underwater observation tower would make the perfect lair for a sea-loving villain.

This legendary urban waterfall creates a dazzling display of rainbows.

This verdant, tree-lined Reykjavik graveyard is both enchanting and eerie.

This exhibit is one of the largest and most well-preserved collections of Jurassic-era trackways in the United States.

This ancient Irish landscape boasts hundreds of legendary ruins.

This museum explores the grim reality of life in the earliest British colonies in America.

This famed Silk Road oasis was one of the largest cities in the world before it was destroyed by a Mongol horde.

Legend says this mysterious stone head belongs to a woman who was petrified by an alchemist.

This fortress played a key role in the battle that would ultimately give rise to the Maratha Empire.

Wander among the abandoned ruins of this once-powerful medieval town.

The unexpectedly beloved remnants of a controversial thermal power plant.

This long-hidden space above Westminster Abbey now displays the battle gear of the legendary King Henry V.

The "Bridge Over the Atlantic" lets you cross the waterway in mere seconds.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.