A bronze plaque marks the site of the only show the "King of the Soul Singers" ever missed.

The arboretum whose marshy soil sucked up the dreams of housing developers.

This Philly landmark has a giant butterfly pavilion, three floors of insect displays, and withstood a $40,000 heist.

Century-old shop, specializing in Occult products.

This beloved marketplace mascot poops money and grants good luck.

A museum dedicated to the strange and extravagant costumes and memorabilia of the mummers, a tradition older than Philadelphia itself.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

America’s smallest national park site is the former residence of exiled Polish national hero Thaddeus Kosciuszko.

Alexander Hamilton’s creation caused quite a bit of controversy.

South Philadelphia is home to Keith Haring's only surviving in situ collaborative public mural.

Erected in 1697 this Philadelphia bridge is the oldest surviving roadway bridge and perhaps the oldest stone bridge in the United States.

The discovery site of the "Capitalsaurus," the official dinosaur of Washington, D.C.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The walls of the iconic dome are hollow and have a secret stairway.

An overlooked monument to the celebrity gangster who helped put the sin in Sin City.

An exotic wildlife habitat right off The Strip.

One of the world's tallest Ferris wheels takes visitors high above Las Vegas in a spinning party room.

On the Fourth of July this area will transform into a Pompeii-like storm of falling embers and ash.

This statue of the "father of television" stands prominently in the United States Capitol.

The tunnel under the Capitol Building where Congress takes out its trash.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

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

There’s a hidden military meme engraved on the World War II Memorial.