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

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

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

A very classy 1920s-era bar right in Grand Central Station.

A masterpiece of LGBT art has been restored in what may now be the most valuable restroom in America.

A room in New York City that contains 250 cubic yards of dirt worth a million dollars.

More gold than anywhere else, ever.

New York City's smallest piece of private property.

A hands-on traveling collection of the innovative devices of yesteryear.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

An unassuming grey box sitting on San Francisco's Pier 17 is a "sky diary" of the coastal city's temperamental weather.

This tall and trim architectural oddity is one of the skinniest buildings in San Francisco.

Chevron maintains one “Standard” brand station per state so it doesn’t lose the trademark.

The sole surviving relic of the San Francisco neighborhood cobbled together from old horsecars and streetcars.

This surreptitious shop is only open five hours per week.

This giant head is all that remains of a once proud statue that survived an earthquake but not a fall off of a wagon.

A mysterious painting of the self-declared Emperor of the United States watches over a local hof-brau.

Forgotten and then destroyed by fire, this was once one of the largest saltwater swimming pools in the world.

Appropriation-friendly collection of books, periodicals, and more.

This print shop boasts one of the largest pinball arcades in San Francisco.

A library built during San Francisco's pioneer times is a student's retreat, bibliophile's sanctuary, and chess player's delight.

A library and museum dedicated to typography.