This monument built by Japanese American immigrants spent decades underground.

Now a pedestrian bridge, this was once part of a narrow-gauge railroad that ran along the east coast of Kauai.

A prehistoric landscape hidden in the cliffs of Maha'ulepu.

Take shelter from Hawai'i's tropical heat under the massive canopy of largest Banyan tree on the island.

A faded sign from the 1920s remembers Baltimore's resistance toward banning alcohol.

This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

FDR's Art Deco hospital tower was hopelessly inefficient.

Live data is transmitted from the Atlantic coast to instantly recreate the ocean waves in this fountain at the NOAA headquarters.

Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

Through the decades, Black music stars have performed at this historic hub for music and the arts.

A gorgeous mural outside a beloved D.C. restaurant pays homage to famous Black Americans.

This poor little statue is the most vandalized memorial in Washington.

An overlooked memorial honoring the local Washington residents who died in World War I.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

Decades before the scandal, this staircase on the river was a literal "water gate."

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

D.C. once had its own tiny rival to the New York Stock Exchange.

The 28,000-year-old specimen is remarkably intact.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

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

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

The U.S. Fish Commission’s effort to mass produce carp.