Croatia's "hairy stone" fortress is one of the most well preserved Istrian castles.

A 16th-century horror show built in a lovely Italian garden.

The bomb-ravaged remains of of a colossal Neptune.

An emerald-green grotto just a short trip from Austin.

A popular swimming hole that hides one of America's most deadly diving spots.

A house of courtship where the Jazz Age's most storied lovers got their start.

A small island hides in plain sight on Austin's Lady Bird Lake.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

The "dragon babies" of southeastern Europe.

Turntable anonymously received orphans, alms, and groceries.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

This Croatian island is for sale but no one is buying due to the dozens of accused Nazi sympathizers who were massacred there after WWII.

A tower marking the spot where Yugoslavia began its resistance against the invading Nazis stands neglected, but not quite forgotten.

Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

This former estate of a fascist leader is now a burnt out ruin leading to a system of secret tunnels.

This scale model of our solar system hid in plain sight for years before a physics team sought out all the planets.

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

Where the lovelorn find a home for their sentimental keepsakes.

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

This massive subterranean fissure is known as the "underground Grand Canyon."

Renaissance villa and gardens complete with a tormented colossus.

During World War II, this rice mill became a Nazi concentration camp.

A wunderkammer of gold and silver reliquaries and ancient saintly bones.