The world's brightest bioluminescent bay.

A two-way chairlift system between Zugliget and the highest point in the city.

A museum in the childhood house of a medical pioneer.

The abandoned "Red Star Train Graveyard" is the final rusting place for precious artifacts of train history.

Museum dedicated to the terror regimes of Hungary.

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

This cheese shop also houses a museum devoted to Dutch dairy.

Museum preserving torture methods from the past.

Collection dedicated to funeral rites, equipment, and mourning rituals of the Viennese.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

This museum promotes informed contraception by documenting its often secret past.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

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

This hidden library of physiological ephemera contains centuries worth of knowledge on the vim and viscera of the human body.

This ruined fort hidden at the top of Central Park can't seem to keep from losing its historical plaques.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

A veritable variety of odds and ends.

A dark, dank room in subterranean Manhattan was the site of a ghastly murder.