Roughly 17 million letters to Santa have found their way to this Arctic Circle post office.

A cathedral resurrected from the ashes of one of Europe's greatest urban fires.

This irregularly shaped sea fortress has defended not one but three different sovereign states.

An abstract monument to a symphonic composer.

A subterranean house of worship carved right out of the bedrock.

This fantastical icy castle is built anew every winter.

An ancient necropolis of magnificent tombs.

For nearly 2,000 years this church has been waging war on local snakes by importing cats.

The ancient mosaics here are considered among the finest in the world, and serve as a stunning record of Greco-Roman daily life.

Late at night, the bust of the "Dracula" actor was snuck onto the facade of this Budapest castle.

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

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A towering spire in the fortress of Kalemegdan honors the victorious armies of Serbia during their struggles against the Ottoman Empire.

A small memorial to a deadly night in Serbia that shook the world before it was swept under the rug.

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

For over 40 years, this quaint little house has teetered on a rock in the middle of a river.

A sinuous path among steep cliffs creates a stunning sight in southwestern Serbia.

Nikola Tesla's ashes are held in a golden sphere, surrounded by his works.

Bridge that died in war and was resurected.

This ominous Albanian fortress houses tanks and downed planes as a reminder of their victories over Western imperialism.

The elliptical citadel resisted the advance of the mighty Ottomans several times, thanks to the military prowess of the "Dragon of Albania."

Hundreds of thousands of concrete bunkers crowd Albania long after the fall of Communism.