A building shaped like the Army Corps of Engineers logo, because why not?

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

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

The oldest continuously operating fish market in the United States.

Largest Roman Catholic church in North America.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

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

A wondrous old library overlooking the nation's capital.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

The United States Capitol's former columns still stand.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

One man's vast collection of artifacts and ephemera from matchbooks and postcards to vintage neon signs and cars.

Home to items never before seen by the public.

This ultra-modern home clings to the slope of the Hollywood Hills on a precarious stilt.

Venue for strange sideshow displays and musical acts.

Former 1954 Del Mar Train Station now serves signature cocktails and delightful culinary treats, and still operates as a Metro stop.

Offering commanding views of the California coastline, this restaurant was a hub for the artists and bohemians of Big Sur.

This stunning sea creature-shaped home blends into the landscape like a fantasy villa.

Once close to extinction, there is no shortage of elephant seals on the beaches of Año Nuevo State Park.

Beautiful Victorian buildings from L.A.'s forgotten architectural past.

The Empire Mine is "one of the oldest, largest, deepest, longest and richest gold mines in California."