The ruins of the bathhouse used by the ill-fated last Aztec emperor still lie in Chapultepec Park.

Many people don't realize there’s a lot going on in—and below—the world’s tallest triumphal arch.

The only castle in North America to ever house European sovereigns.

A jaw-dropping "megalibrary" that turns book-browsing into a geometric adventure.

Frida Kahlo's childhood home, now a museum of her life and works.

An island filled with hundreds of hanging, decomposing, decapitated dolls.

A band of aerialists and circus performers putting on incredible shows in East Williamsburg.

Lie in a hammock where George Washington stood.

Love, knishes, and best wishes from this legendary Lower East Side bakery.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

Leaf through over 30,000 artists' sketchbooks in what may be the world's largest collection of doodles

Tucked in a nondescript downtown Brooklyn mall is a bar containing a remarkable turn of the century anatomical wax collection last seen in 1920s Berlin.

Sniff the Titan Arum's rotting flesh.

Behind a bodega is a small museum of relics and ephemera showcasing the history of New York.

Mysterious 500-year-old tapestries depict a unicorn hunt.

The one-stop shop for all of your superhero (or evil arch-nemesis) needs.

Elevated freight railway turned wildly successful urban park.

This hilltop park offers magnificent views and a Frank Lloyd Wright masterpiece.

The final resting place of a space program monolith.

Scores of vintage street lamps shine along L.A.’s Miracle Mile.

Historic funicular railway, believed to be the shortest railroad in the world.

These delicate buggers are some of the rarest fossils that have bubbled up from the Tar Pits.

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

America's most famous piece of self-built architecture.