Built as an anti-fascist tribute, this surreal Yugoslav memorial became an unwelcome symbol after the Croatian war for independence.

This military tunnel dates back to World War II and provides visitors with a little wartime adrenaline.

The only gulag ever to exist in socialist Yugoslavia.

Humble beginnings for one of the world's most famous scientists.

Legend has it fairies gathered at the site of this medieval castle.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

A wonderfully strange collection of 500+ stuffed frogs doing people things.

The complex has been abandoned since the Croatian War of Independence, barring a stint as a set for 'Game of Thrones.'

This truly palatial work of Communist-era architecture now sits crumbling on a Croatian beach.

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

A musical instrument played by the sea.

An ethereal glowing blue ocean cave in Croatia.

Gigantic mosaic sculptures of the figures on Tarot cards fill this colorful Tuscan garden.

Walk through a fairytale in Tuscany.

One of the largest caves in the world open to the public.

This Tuscan lake hides a 13th century town that is still visible when the water recedes.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

This abandoned Brutalist treehouse is a hidden architectural relic.

This magical-looking island is notorious for the misfortunes suffered by its owners.

A fairytale island floats in the middle of Italy's little-known Lake Orta.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.

These "anatomical machines" are only one of the many strange items in this Italian crypt.