Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

A wonderfully strange collection of 500+ stuffed frogs doing people things.

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

The world's newest astronomical clock is also its most accurate.

A unique hotel for the artistic soul.

A perfectly preserved hill village where the buildings are painted like white lace.

The 700-year-old fortress was the site of Count Orlok's castle in "Nosferatu."

Backwards hour and minute hands and a timing mechanism that fluctuates with the temperature led to this clock tower's local nickname.

A Serbian monument to plums.

These unique sculptures form a musical ensemble of recycled metal.

The final resting place of one of the first alleged vampires.

At this archaeological site, visitors can explore the ruins of the capital of the former Roman province of Moesia.

Once a beautiful palace, this structure is now known as the ''museum of destruction."

This natural spa is known for its healing properties and vibrant hue.

This historical village takes you back to the 19th century.

This fresco inside a Serbian cave church has been a source of disagreement.

Stone age urban planning.

An idyllic traditional timber village on a picturesque hill was built for a film.

These natural stone bridges are the largest on the European continent.

An eerie, protected forest of old-growth oak trees, many of which are now dead.

A hidden stream deep in the mountains creates one of the largest tufa waterfalls in Serbia.

The ridged layers that make up this river canyon represent Earth's geological history.

Through the colossal entrance to this cave you'll find limestone tubs and an underground waterfall.

This mesmerizing medieval monastery-cave complex sits thousands of feet above ground overlooking a valley.