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

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.

Railroad officials in the early 1900s sought to spare travelers the sight of Roman soldiers’ private parts.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

This groundbreaking 16th-century map is known as "America's birth certificate."

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

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

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

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

This unassuming passageway played a key role in one of the most important events in U.S. history.

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

Over the last century, this elegant columned facade has been home to the headquarters of a bank, several nightclubs, and a restaurant.

This Masonic lodge was the first major private building to be constructed in Washington, D.C. after the Civil War.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

Go take a picture with the inventor of the daguerreotype photographic process.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

A much-maligned monument to teetotalism.

It was once the base for a series of domestic terror attacks.

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.