Though math nerds may not be the first demographic you'd expect to turn out in droves for an afternoon spent outdoors walking block after block, mathematician Glen Whitney has begun leading guided tours of Manhattan. Whitney, who quit his job at a hedge fund, has attracted a nice following: This week's New Yorker carries a dispatch from writer Nick Paumgarten on one of Whitney's tours, which that day took a group from 66th Street to Columbus Circle while stopping for all sorts of hidden math-yness along the way. When the group reached 64th Street, for instance, Paumgarten describes how "a Philip Johnson clock just off Columbus Avenue led to a disquisition on Pythagoras, octaves, calendars, eclipses, and time." Whitney is using the tours in hopes of building demand for a math museum in New York, and—for a city that already has museums devoted to sex, comic books, and creepy wax statues—why not? After all, for those who want nothing to do with any of that complicated number-learnin', there's always the Gossip Girl bus tour.