The Habsburgs' royal collections of art and wonders.

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

Op-art architecture designed for happiness.

The topiary maze at the Habsburg hunting lodge.

Now harmless, this looming post struck fear into the heart of medieval troublemakers.

Colorful concentric circles honor a small Croatian town's supposed spot at the nucleus of it all.

An ancient knight and a symbol of the city's freedom.

Island wonderland for communist autocrats.

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

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

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

Gargoyle head that brings good luck.

This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

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

The remains of a sunken military ship wreck visible through clear water.

Where the lovelorn find a home for their sentimental keepsakes.

A musical instrument played by the sea.

One of the world's tallest statues is also one of its most hated.

Former headquarters of the KGB.

A sculpture park of the tossed aside relics of the USSR, from Stalin to a massive Soviet emblem.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.

Founded in 670, this ancient mosque is an architectural time portal.