Inside this Krakow church, an explosion of psychedelic color.

The final resting place of the author who gave us the Little Mermaid, the Ugly Duckling, and many more beloved fairy tales.

For over a century, it has been a tradition to raise a flag at the top of this 450-foot sandstone pillar on the 4th of July.

Take a dip in the world's largest mineral hot springs pool.

These markers are used to document elevation changes around the famed dam.

A natural swimming hole that was once a ceremonial center for Mayan priests.

Sparkling, calcite-covered skeletons of children who may have been sacrificed to appease an angry god.

Giant heads occasionally litter the industrial Houston neighborhood where sculptor David Adickes has his studio.

The graveyard holds the remains of Irish immigrants who arrived in Queens after fleeing the Great Famine.

Overlooking the Colorado Convention Center is this giant sculpture made from thousands of triangles.

To find the "unicorns of the deep" you've got to go downstairs.

At Chicago's revered Field Museum, visitors are invited to learn about and literally explore DNA.

These pretty kitties killed and ate as many as 135 railway workers.

A spectacular remnant of an Adler and Sullivan masterpiece that was destroyed in 1972.

Chicago's Navy Pier on Lake Michigan was a training hub for aircraft carrier pilots during WWII.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

A 400-foot-tall tall map of Chicago makes this once-ignored building stand out.

Illegal drag racing two stories beneath Chicago’s streets.

The iconic Chicago sculpture hides a beautiful and easily overlooked plaque on the backside.

This memorial plaque remembers a strangely shallow maritime disaster known as "Chicago's Titanic."

Each of these gorgeous, intricately decorated rooms is painstakingly crafted to the scale of 1 inch: 1 foot.

Once at the center of U.S. finance, the historic Trading Room was meticulously recreated piece by piece and rebuilt in the Art Institute.

Fragments of architectural wonders from around the globe are embedded in the newspaper building's walls.

A shining sculpture made of 3,115 lights, the number of visible stars in the Northern Hemisphere.