Mutant vegetables, transgenic mosquitos, and atomic rodents span the walls of this one-of-a-kind museum.

This supper-club-turned-concert-venue still serves drinks at its original rotating bar.

The site of an ancient Mississippian settlement that appears to have flourished during the 10th to 13th centuries.

Advice-columnist's bell tower, paid for with pennies.

The site of the one of the most deadly train wrecks in American history.

This defunct, fortress-like prison has been the setting for several movies.

California's largest steel arch bridge.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

She stares out across six lanes of traffic, clutching a musket and infant with determination.

FDR's Art Deco hospital tower was hopelessly inefficient.

This mighty white oak in Bethesda survived both the American Revolution and the construction of Washington D.C.'s metro red line.

The location where the famed author and abolitionist began his journey to freedom.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

A historic arena where the Beatles played their first concert in the U.S.

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

The only Leonardo Da Vinci painting in the Western Hemisphere.

This large garden vase urn has nothing to do with the seventh U.S. President—it was designed by one landscape designer to honor another landscape designer's contributions to the National Mall.

A computer bug so primitive it was an actual insect.

After James Madison's death, his wife and former First Lady Dolley Madison lived in this yellow building near the White House.

Before Nixon, "watergate" meant canals.

A portal into the bricked up canal that runs through the heart of Washington D.C.

The word "Watergate" will forever be associated with the infamous scandal in 1972, but this fountain is famous in its own right.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

A historic ruin just 20 feet away from a busy highway onramp.