The walls of the iconic dome are hollow and have a secret stairway.

A long lost multi-cultural music venue used to reside in the bottom floor of Chicago's Flat Iron Building.

This abstract sculpture is rumored to cast a hammer-and-sickle shadow once a year.

Orthodox church partially financed by Tsar Nicolas II.

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

This landmark cemetery in Boston was created more than 300 years ago.

Perhaps the tiniest sculpture in Saint Petersburg is a little bronze finch inspired by a song.

Inside the world's largest seed bank, WWII botanists elected to starve to death rather than compromise their collection.

A scale model of Russia so big visitors are offered binoculars to rent so they can see the whole thing.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.

Gargantuan home of Russian science.

Stalinist skyscraper built with help of cryotechnology.

The tallest hotel in Europe.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

World's largest bell sits on the grounds of the Kremlin in Moscow.

Former headquarters of the KGB.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

This alley in downtown Chicago held the bodies of over 600 people after the fateful Iroquois Theatre fire.

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

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

This $3 million model train takes you through Chicago, Seattle, and the thousands of miles in between.

A gothic church spire sits atop this skyscraper, the tallest church in the world.

One of the steepest streets in the United States makes an intriguing challenge for cyclists.

What was once a true peninsula has now been filled in, causing the water to recede and leaving many streetside "waterfronts" and landlocked "islands."