Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

A clone of a cloned tree that was so important it allegedly had its own guards.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

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

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The most decorated dog of World War I is preserved in the Smithsonian.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

A wondrous old library overlooking the nation's capital.

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

The United States Capitol's former columns still stand.

The only home that Alexander Hamilton ever owned has a history almost as troubled as his own.

A Manhattan courthouse hides a small but scathing memorial to Holocaust injustice.

The walls are decorated with whimsical murals painted by the creator of the Madeline franchise.

A dark, dank room in subterranean Manhattan was the site of a ghastly murder.

The final resting place of the great escape artist, where some still gather to wait for his escape from death.

An uber-secure, windowless tower of doom in the center of Manhattan is an NSA spyscraper.

The original toys that inspired the beloved children's stories are on display at the New York Public Library.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

A masterpiece of LGBT art has been restored in what may now be the most valuable restroom in America.

The oldest operating apothecary in the US has treated everyone from Thomas Edison to Mark Twain.