In midsummer, Central Park's Great Lawn can look more like a nudist colony than a place to work up a sweat. But in these early fall days, as sunburnt refugees scurry indoors, the city's largest swath of green space is an ideal place to pump up your forehand, test your cliffhanging ability, and hone other skills you didn't get around to sharpening this summer -- all for free, or close to it.
Tennis: Waltzing to the front of the Tennis Center line is allowed if you've invested in a $50 season permit (available at The Arsenal or Paragon Sports) and a $5 reservation ticket (from the Tennis Center). Racket rentals are $5 per hour; private lessons are $43-$48 per hour. Or sign up for weekend mini-camps ($135 for up to six hours), taught in groups of four.
Biking: Cruisers, 21-speeds, and tandem bicycles rent for $9 to $20 per hour at the Loeb Boathouse. With enough practice, you should have the rest of the Center Drive herd quaking in your wake.
Rock climbing: Explore your vertical limits on the climbing wall at the North Meadow Recreation Center -- not quite as challenging as what you'll find at some gyms, but far cheaper ($5 a day or $50 per year, including equipment; open on Thursdays and Sundays). Learn the ropes with four three-hour lessons on the wall ($200). For a twist, try a 90-minute bouldering class (moving sideways across the rock face, $50).
Fishing: At the Discovery Center, you can borrow bamboo poles and bait for catch-and-release catfish and bass fishing in the Harlem Meer at the northeast corner of the park (11-4:30; closed Mondays).
Chess: Or stop by the Dairy and pick up pieces that you can use to play on the boards at the nearby Chess and Checkers House (10-5; closed Mondays).
Bird-watching: Belvedere Castle also loans guidebooks and binoculars to those who want to check out migrating hawks on the Ramble -- or the last few sunbathers (10-4:30; closed Mondays).
Paragon Sports, 867 Broadway, at 18th St. (212-255-8036). In Central Park: Tennis Center, near Central Park West and W. 96th St. (212-280-0201); The Arsenal, 830 Fifth Ave., at 64th St. (212-360-8131); North Meadow Recreation Center, mid-park, at 97th St. (212-348-4867); The Dairy, mid-park, at 65th St. (212-794-6564); Charles A. Dana Discovery Center, near Fifth Ave. and E. 110th St. (212-860-1370); Belvedere Castle, mid-park, at 79th St. (212-772-0210); Loeb Boathouse, near Fifth Ave. and E. 74th St. (212-861-4137); www.centralparknyc.org.
PLUS: This Week's Sale Picks