Herb Lester Associates makes pocket-folding city guides for what guidebooks ignore, and this one maps the Paris underground: catacombs, wartime bunkers, wine cellars, abandoned métro stations, and medieval wall fragments. Printed as ten A5 panels on heavy stock that fold to jacket-pocket size, it covers both the famous Denfert-Rochereau ossuary and obscurities like a bank-vault door beneath the Champs-Élysées. It’s a guide to a city most visitors walk above without knowing it exists below them.