The largest drain hole in the world.

The only standing town in the United States that early Chinese Americans built for themselves.

I Street Bridge is the heaviest swinging center bridge in the United States.

A replica of the first public theater built in California.

This 19th century train workshop is a treasure trove of railroad history.

The California capital city once stood 10 feet lower than it does today.

Where the first "expert riders, willing to risk death daily" for the Pony Express were recruited.

This 15-story mural celebrates the 50th anniversary of the musician's iconic "At Folsom Prison" album.

The site of a fallen tree that protected Americans from British forces during the American Revolution.

This secluded ruin was once a home for exotic plants.

You can still ride this 100-year-old work of art in Brooklyn's largest public park.

A grand New York post office that is home to mailman Santas, scraps of postal history, and a pneumatic mail system.

This eclectic sculpture garden in Brooklyn, home to a bizarre collection of art, was once a run-down junkyard.

The place where Dvořák composed some of his most famous works.

This elaborate tunnel is the first structure composed of cast concrete in the United States.

Outstanding taxidermy dioramas showcase the grandeur of the continent's wildlife with spooky realism.

This old estate is a remnant of when the Bronx was a popular summer destination for wealthy New Yorkers.

Once considered the height of medical modernity, this structure is now the oldest remaining component of Roosevelt Hospital.

This recipe is set in stone.

A hidey-hole sandwiched between cellphone, DVD, and jewelry stores features Tibetan delights.

This small and serene place for quiet reflection on Staten Island was built in China based on the gardens of the Ming Dynasty.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

A Romanesque sanctuary of calm amid the bustle of downtown Los Angeles.