Volcanic stone sentinels stand watch at a Korean Bell Garden in Virginia.

This church built atop a gas station promises to "equip you for the next stage in your life’s journey."

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

Deep in the forest of northern Denmark, this secret underground bunker was built at the height of the Cold War.

The northernmost point in Denmark is a turbulent sandbar created by two clashing seas.

Tiring of digging out the door to this church for every service, it was eventually abandoned to the sands.

The castle used by the Danish Royal Family as a hunting retreat.

An aptly-named street near the birthplace of the modern LGBT rights movement.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

Order scoops of pandan, lychee, and black sesame at this family-run institution.

This wall on a street corner in Lower Manhattan has been a blank canvas for a rotation of renowned artists since the 1980s.

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

The notorious headquarters of a corrupt political machine.

The most confusing clock in New York.

A menagerie of concrete animals brought together from across New York City's parks.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

Manhattan's deadly West Side railroad, which killed hundreds of New Yorkers, is remembered by this simple plaque.

This bronze sculpture was inspired by a photograph of Martin Luther King Jr. and his wife embracing after he won the Nobel Peace Prize.

Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

An old pay phone rewired to play local bird calls and songs at the press of a button.

Press 1 for knock-knock jokes.

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

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

The "lovely red Vega" of the legendary record-settling pilot.