The world's third-largest crystal sphere has sat in the Penn Museum since 1927 with the exception of one outlandish theft.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

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.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

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

A spectacular tribute to statesman and philanthropist Andrew Mellon.

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

America's first public mental health facility.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

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

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

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

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

Civil War soldiers, captains of industry, and paupers all interred on historic grounds.

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

The phrase "the shot heard around the world" was coined after a skirmish at this bridge.

The second-tallest water tower shaped like a peach in the American South.

A collection of huge Pre-Colombian structures in Alabama.

Every last book in this bookstore is signed by the author.

Enjoy an overnight at an old haunted B&B site of the Borden family murders.

A simple but powerful tribute to the 20 victims of the 1692 witch trials.

Located just behind a quiet residential neighborhood, this is ground zero for the Salem witchcraft hysteria of 1692.

A glimpse at Walt Disney's vision for a "community of tomorrow," in miniature.