A World War II evacuation tunnel turned into a history display of Croatian state and people.

Two buildings named after their windows that make it look like a sea of television sets plastered to a wall.

This feat of Brutalist architecture is also known as the Three Sisters.

This art installation pays homage to the famed stones of European lore.

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

Different sections of the Zemun Fortress were built in the 14th and 15th century as a response to the advance of the Ottoman Empire.

A Serbian church lit by chandeliers made of weapons.

In the hinterlands of Serbia's capital, a giant reflective mushroom houses an aeronautical history of the former Yugoslav republic.

A swirling spectrum of stained glass dazzles visitors who enter this subway station.

City law dictates that this mountaintop cathedral containing the heart of a saint is to remain the tallest building in town.

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

A pair of connected skyscrapers form this symbolic gateway.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

The highest point in Washington state is a volcano covered in glaciers.

Oregon's unexpected high desert, displaying layers of time in a colorful show.

This large, castle-like structure is hidden amid the mountains on the grounds of the Utah State Hospital.

A volcanic core jutting above the plain between the Snake and Boise Rivers, a marker identifies the reference point for all U.S. Government Surveys in Idaho.

The only bridge in the United States where BASE jumping is legal without a permit year-round.

An impressive waterfall nestled in the cliffs of Idaho's Snake River Canyon.

One of the "twins" in these falls on the Snake River was sacrificed for hydropower generation in the 1930s.

This underground cave located in the most barren reaches of Idaho is filled with ice year-round.

These falls, sometimes called the "Niagara of the West," still put on a good show at the right time of year.

This pristine World War II airfield gives a comprehensive look at atomic development and aviation history.

Although it also features red, orange, and variegated cliffs of Navajo Sandstone, this state park is often overshadowed by its more famous neighbor.