Raging waters have created a strange geological site that looks like something off of a progressive rock album cover.

The smaller of the three towers of San Marino is a former prison inaccessible from the ground level.

The townhouse where the "Blood Countess" Elizabeth Báthory started her murderous career.

Baroque celebration of the end of the Great Plague of Vienna.

Op-art architecture designed for happiness.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

The final resting place for the remains of 143 Habsburg royalty.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

The beautiful baroque library of the Hapsburg empire.

While not Turkey's deepest underground city, this subterranean redoubt is the largest.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

This historic hotel preserves many treasures from its heyday hosting passengers on the Orient Express.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

Legend says if you stick your thumb in the hole and it gets wet, your wish will be granted.

The most metal church of all time was built in record time because of an international, pious pissing contest.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

The ornate miniature mansions were built for Istanbul's feathered residents.

A marvel of Byzantine engineering under the streets of Istanbul.

The eclectic home of a leading Turkish architect is a gorgeous piece of eye candy.

A space dedicated to contemporary art and culture, co-chaired by fashion icon Miuccia Prada.

Before there were doorbells this bronze ear was installed for visitors to announce their arrival.

The secret medieval communication system will whisk your words above the noise of the crowd.