Over a thousand feet beneath the Detroit streets is a subterranean metropolis few are allowed to enter.

This railway-turned-greenway provides a pedestrian link in downtown Detroit and celebrates urban artwork.

This "Palace of Purification" has made many film appearances as a dark and sinister headquarters.

The oldest landmark of Toronto is a testament to shifting sands.

Lost subway station nestled beneath Toronto's busy commuter line.

A well-preserved network of cavernous tunnels have spent silent centuries removing Toronto's waste.

A frozen relic of Seattle's hydroelectric boom is now a teaching facility for future engineers.

The spur that wouldn’t die.

The historic bar where local ship captains, traders, and gold miners would come together to do business a century ago.

A nondescript Seattle restaurant inherited a piece of European history.

The tech giant built three enormous glass orbs in Seattle so employees could work inside a rainforest greenhouse.

This former coal gasification plant found a curious second life as a popular public park.

A huge musical sculpture and other art installations on the National Oceanic and Atmospheric Administration grounds.

The only home that Alexander Hamilton ever owned has a history almost as troubled as his own.

This Wall Street bar was once a hub of revolutionary activity where Washington famously bid farewell to his troops.

The oldest house in Manhattan is now a museum that remembers the home's sordid history of scandals, vice-presidents, and ghosts.

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

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

A crumbling hospital from the 1850s on Roosevelt Island.

If New Orleans is the birthplace of the "cocktail," why does their own museum of cocktail memorabilia beg to differ?

The only rotating bar in New Orleans has been slowly spinning since 1949.

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

A restaurant and observation deck built in a unique broadcasting antenna.