Everyone from Mark Twain to Teddy Roosevelt has a pipe hanging from the walls of this historic chophouse.

Avoid gangster interaction while window-shopping.

The last slot car racing arcade in Brooklyn is keeping the dream of speedy little autos alive.

Unique antiquarian shop specializing in globes, maps, and prints.

More gold than anywhere else, ever.

This little museum is built on a theater that was once a wildly elaborate speakeasy.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

This lower Manhattan bar is set up in an old bank vault that rests beneath a skyscraper that hides even more historic splendor.

A semi-scholarly approach to sex.

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

Dodge prohibitionists and slide through the telephone booth in Crif Dogs.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

A crumbling hospital from the 1850s on Roosevelt Island.

A terrific purveyor of natural history objects and curios.

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

Nestled on the banks of a river in Nuremberg is a small museum that was once home of the city's official executioner.

Dress up like a miner and take a slide into the disco-lit depths of this once foundational salt mine.

An abandoned train station in Munich constructed for the 1972 Olympic games.

Model Trains and Much More in Hamburg.

Hamburgers are intensely proud of their tunnel beneath the river.

Wax models of disease and deformity are on display at this German medical museum.

This museum housed in a former brothel explores the past and present of sex work in Amsterdam.

This pirate-broadcasting-tower-turned-restaurant played a rebellious role in the history of Dutch television.

Famed for its pie, this eatery has a hidden tunnel that allowed Catholics to secretly walk to church during the Reformation.