Part of a WWII submarine is lurking outside the Washington Navy Yard parking lot.

The first memorial dedicated solely to the Black troops who fought for the Union.

Amid the sprawling Defense Intelligence Agency Headquarters is one of Washington's least accessible museums.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

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

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Home to items never before seen by the public.

This contorting sculpture is the tallest in San Francisco.

These WWII-era murals were initially booed as a libelous portrayal of the American dream but have survived multiple attempts to have them destroyed.

This grinning pup statue is all that's left of what was once a ubiquitous Bay Area diner chain.

This Japanese treats shop may have been the first business to mass-produce fortune cookies in the United States.

Guns that have been defending San Francisco since 1904.

Faceless white figures loom over the city from the rooftop.

The only visible piece of San Francisco's most famous shipwreck.

This partially buried wreck is one of the most complete of its kind but is only revealed when the sea allows.

Big gun installations, built over a massive cemetery, now abandoned & hidden in trees.

A 300-ship graveyard, with a few still visible at low tide.

Visible below the waves are memorials to the city's Gold Rush dead.

Tiki luxury on Nob Hill.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

An effigy of Vancouver's Gastown neighorhood's namesake.