The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

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

A tiny church on a man-made island in the Adriatic.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

A pair of connected skyscrapers form this symbolic gateway.

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

A misnamed well, with a deep dark past.

A Serbian church lit by chandeliers made of weapons.

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

Oriental bazaar in the heart of Sarajevo.

This historic timepiece is thought to be the only public clock in the world that keeps lunar time.

Bridge that died in war and was resurected.

The place where World War I began.

A number of craters left by fatal mortar strikes have been filled with red resin to remember those lost during the Siege of Sarajevo.

A musical instrument played by the sea.

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

An eclectic art form practiced by untrained masters is celebrated at this museum in the heart of Zagreb's old Upper Town.

Where the lovelorn find a home for their sentimental keepsakes.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

The "dragon babies" of southeastern Europe.

A miniature train-ride through Slovenia's largest cave system.

A whimsical bridge adorned with decorative dragons.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world’s largest coastal brick fortresses.