Map room at the New York Public Library

It starts with a simple question: Got any old maps of Brooklyn? An hour later, I’ll still be poring over a stack of them, losing track of time, as it’s so easy to do in the Lionel Pincus and Princess Firyal Map Division of the New York Public Library. For all the apparent stuffiness of the ornate Beaux Arts room, you can stroll in and look at almost any of the collection’s 431,000 sheet maps and 16,000 atlases. There are German army maps from World War II and antiquarian cartography ones, but I get the most buzz examining the 20,000-plus maps of New York. A giant 1782 British Headquarters Map used during the Revolution shows forts, hills, ponds and a small settlement below a wall at Manhattan’s tip. An 1880 atlas transposes the modern Brooklyn grid onto the original topography and later farm lots, so you can see that a winding Road to Gowanus would have bisected Smith Street, and that Luquer’s Mill Pond covered much of Red Hook. Geeks can even consult a directory to see who lived where—yes, there was a Bill the Butcher in Five Points. “You don’t have to know anything when you come in,” says Alice C. Hudson, chief of the Map Division. “Just tell us what area you’d like to know about.” Within minutes the easygoing librarians can produce a sequence of maps showing a neighborhood’s vertical history. Want one to keep? They can scan and print a copy for $30. Take that, Google.

—Rebecca Dalzell

Lionel Pincus and Princess Firyal Map Division of the New York Public Library, Fifth Ave at 42nd St, room 117 (212-930-0587, Tue, Wed 1--7:30pm; Thu--Sat 1--6pm; free.