Hot Doug's "Hot Dog" Stand.

These chunky stone towers out in Lake Michigan are the key to Chicago’s drinking water.

The unluckiest U-boat in the entire German fleet is now on display in a Chicago museum.

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

An easily overlooked memorial to a Ukrainian famine-genocide that killed over 4 million people.

Need a hardcopy of the 50-title Code of Federal Regulations? This is the place.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

The fierce beast perches atop a pedestal marking where the historic City of London gates once stood.

This crumbling medieval basilica once attracted pilgrims by the thousands to collect a miraculous dust that formed above the saint's tomb.

The remnants of a creative early method of wildfire prevention.

One of the oldest of its kind.

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

The first bell ever cast in Boston was cast by Paul Revere...and sounded terrible.

This area was once known for being a lawless haven for rough-and-tumble sailors, earning the maritime-themed nickname "the black sea."

One of the indelible moments of the American Revolution took place at this location.

A sculpture of the famous photograph stands on San Diego's "Greatest Generation Walk."

This Soviet statue is based on a piece of propaganda that's been elevated to national myth.

Lone survivor from Custer's Last Stand forever preserved.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.

Final resting place of Geronimo, Quanah Parker, and the first atomic gun ever fired.

A small triangle of DC grass is the final resting place of one of Sonny and Cher's songs.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.