America's most famous piece of self-built architecture.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

Thanks to a quirk of elevation this gift shop produces magic doughnuts that are found nowhere else on Earth.

The US Navy's only submarine museum is also home to the world's first nuclear submarine.

Holding multiple historical boats and an entire 19th century village, this New England attraction is the largest maritime museum in the world.

A scenic fort on the harbor protected Philadelphia from an attack that never came.

A historic presidential getaway on the continental United States' southernmost island.

The museum chronicling a treasure hunter's dream, fulfilled.

A monument celebrating the idea of reaching inaccessible places.

Florida's oldest bar was once a morgue, complete with a hanging tree and gravestones.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

The remnants of the fortress that saved Georgia from the Spanish still stand guard on their swampy island.

The only royal palace on U.S. soil has been a territorial capitol, a military headquarters, and a prison for a queen.

An authentic replica of an Asian temple and garden hidden amongst the natural beauty of Hawai'i.

The lowest point in the state of Illinois, at the confluence of the Mississippi and Ohio rivers.

Known as the "Cross At The Crossroads," this massive metal cross is just short enough to avoid the FAA.

You have to love a museum with a truly dedicated focus. A focus on Superman, for example.

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

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

The only Bahá'í house of worship in North America and one of only a handful worldwide.

A collection of outdoor art by renowned muralist Robert Dafford depicts the history of a flooded city.

Kentucky's anomalous peninsula projecting into the Mississippi River, site of legendary earthquakes and local feuds.