UNESCO-protected ancient burial ground.

A spectacular Bulgarian cave resembling a devil's head with a waterfall rushing down its throat.

This tiny Bulgarian town offers a stunning location in the mountains and a storied history.

Bizarrely shaped rock formations in northwest Bulgaria come with equally bizarre legends.

An architectural marvel that spans the Arda River, and has stories of a haunted past.

An abandoned saucer-shaped monument in the Bulgarian mountains.

One person's lost luggage is another person's treasure.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

Upside-down trees serve as natural flower pots in this hanging garden of Alaska.

The ghostly remains of what was once the world's richest copper mine.

Mind-blowing carvings and fantasy ice scenes grace the largest year-round ice environment in the world.

This whimsical stacked cabin looks like something out of a children's book.

A psychedelic labyrinth on the San Francisco bay.

An industrial site turned into Hungary's most cherished natural wonder.

This quaint Hungarian railway system is operated exclusively by children between the ages of 10 and 14.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

Museum dedicated to the terror regimes of Hungary.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

This disappearing geyser has been attributed to witchcraft, but really it's all about rainfall.

Mysterious craters may have been home to an ancient cult.

The ruins of an Estonian prison are drowning in the quarry lake where the convicts were once forced to work.