Once the home of a hermetic monk, this cave now houses a small church.

Museum dedicated to the terror regimes of Hungary.

Launched by Napoleon's soldiers more than 200 years ago, a cannonball remains embedded in the tower wall.

The beautiful baroque library of the Hapsburg empire.

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

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

A magnificent collection of imperial armor and weaponry.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

The most decorated dog of World War I is preserved in the Smithsonian.

This 900-year-old mosque was restored using traditional techniques and materials.

Parts of this palace are upheld by merely palm stems or reeds supported by palm tree beams.

Abandoned station along an ancient pilgrimage route.

This fortress sits atop a centuries-old well system.

This giant volcanic crater holds its very own field of salt.

A 19th-century fortress and collection of artifacts offer a tour of Saudi history.

Once a major stop on the Hejaz Railway, this desert station (complete with steam locomotive) has been abandoned for decades.

These towering cliffs jut dramatically from the middle of a barren desert.

Village of slate houses, built on a white marble outcrop.

A historic structure that once housed pigeons used by farmers to help fertilize farmland.

The Arctic Archipelago is home to world's largest third order island: an island in a lake on an island in a lake on an island.

The highest tides in the world come in and out here twice a day, allowing you to essentially walk along the ocean floor.

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.