The oldest remaining building in Tacoma was once the home of the "oldest bell tower" in America.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

Try not to get slimed in Tribeca.

No one knows how this Pacific Northwest spruce tree came to have so many trunks.

All aboard the world's longest miniature railway.

Huge concrete structures designed as an early warning system for Britain to detect enemy aircraft.

A line of abandoned, alien-like fortresses dot the mountains of North Italy.

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

A massive, secret marina for the Nazis' most formidable weapon in the Atlantic.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

An abandoned bus station transformed into a museum dedicated to the history of Greyhound Lines, in the place where it all began.

This historic building provides a powerful glimpse into the lives of Japanese Americans forced to relocate during World War II.

Designed by Maya Lin, the memorial honors 41 individuals who died fighting for equal rights between 1954 and 1968.

Twice a year, visitors can tour the desolate site that birthed the Atomic Age.

A living snapshot of a different time in America is preserved and maintained by a community of volunteers.

The site of one of Japan's very few American occupations during World War II still holds the relics of a roundly disastrous campaign.

The highest point in Arizona is an oddly snow-topped peak within the otherwise arid state.

An unassuming secret door once led to a legendary watering hole.

The tragedy of the Japanese internment camps is remembered here by a stark "Soul Consoling Tower."