This woodland architectural installation acts as a camera obscura for the heavens.

This scented city oasis was a labor of love.

The story behind this beloved toy—named for Theodore Roosevelt and owned by his grandson—is more complicated than you might guess.

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.

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

Look closely and you’ll notice that the color changes a third of the way up the tower.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

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

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

Washington's iconic carousel has a nice piece of Civil Rights history.

Perhaps the most scandalous statue of America's first president.

Largest Roman Catholic church in North America.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Home to items never before seen by the public.

One of the oldest living oak trees in the Southeast.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

A grand Gothic Revival basilica with stained glass depictions of Montreal's religious history has only one soul resting in its crypt.

These artifacts were discovered during the construction of the airport, with some dating back to the Neolithic period.

This curious, round temple is the oldest still-standing marble building in Rome.

This ancient market is often referred to as the oldest shopping mall in the world.

Virgil's many-mouthed gateway to the underworld.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

This domed temple was built in a hidden cave mouth as a refuge for sinners seeking absolution.