A psychedelic labyrinth on the San Francisco bay.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

Willy Wonka would love this weird half-a-home.

This upscale streetwear store is hidden behind a fake Snapple machine in the back of a deli.

A curious collection of miniatures in a quiet corner of the Chicago Children's Museum.

This historic hotel invented the chocolate brownie.

All of Chicago's wood-paved streets are long gone but two alleys remain.

A century-old network of freight tunnels underneath the city's historic business district.

This morbid, delightful curiosity shop offers everything from animal bones to human teeth.

This shop for all your super spy needs hides an educational secret.

These ornate manhole covers were used for a now-forgotten purpose.

Red frames showcase remnants of one of New York's original subway stations.

There must be a pun in this haystack somewhere...

The name of this tiny pocket park tucked between two buildings on Manhattan's Upper West Side is Latin for its location: "seventy-one."

A Manhattan office building is home to the world's largest chess board.

Phil Mortillaro uses keys to bring art back to the Village.

A discreet little stairway on St. Nicholas Avenue leads to a quaint and unexpected cobblestone street of 19th century wooden rowhouses.

A bit of retro transportation flair preserved in the world's largest department store.

During the holidays, a vintage subway train whisks New Yorkers back in time.

A Manhattan courthouse hides a small but scathing memorial to Holocaust injustice.

Spinning silently in the lobby of an Art Deco masterwork is a massive vintage model of the Earth.

One of the last Jazz Age "Wonder Theaters" in New York City.

A WWI fighter plane and turn-of-the-century penny candy shop are among the unexpected features of this Financial District building.

This semi-hidden Manhattan restaurant is based out of a loading dock.