An 18th-century Spanish watchtower made entirely of seashell and concrete.

A building so large that it has its own weather.

This abandoned NASA launch site is now a memorial to a trio of astronauts who were killed there.

One-time winter retreats of prolific inventor Thomas Edison and his friend Henry Ford.

A time capsule of Floridian history fights to survive on the banks of Chokoloskee Bay.

This sculpture of a bowler hat is complemented by a matching umbrella a few blocks away.

This downtown Dallas art installation is always on the lookout.

The 25th President's marble casket can be visited in this classical Ohio tomb.

This extraordinary Depression-era expenditure was modeled after a postcard of a Mediterranean hotel.

This magnificent herd of stampeding elephants has been frozen in time for over a century.

Outstanding taxidermy dioramas showcase the grandeur of the continent's wildlife with spooky realism.

There must be a pun in this haystack somewhere...

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

This outdoor gallery of graffiti-covered walls pays homage to the past, present, and possible future of street art.

One of the most enjoyable bits of history at Coney Island and “the most romantic ride in the world.”

This small pedestal marks the spot of the first lot of land sold in Alexandria, Virginia in 1749.

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

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

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

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

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

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.

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.