Starting July 10, the Summer Sunset Rooftop Yoga class meets on the roof of the Greenwich House ($20; 27 Barrow St., nr. Seventh Ave.; 212-414-2903) at 7:30 P.M. Be sure to preregister, as it fills up quickly.
Riverside Park South gives free Pilates classes at 6:30 P.M., through mid-August (212-408-0219). Bring yourself and a mat to the plaza at 66th Street.
Show up with a mat to a Sunset Yoga class (pictured) at the Empire-Fulton Ferry State Park in Dumbo (July 5 and August 2, at 6:30 P.M.; 718-624-5525).
The Tai Chi Chuan Center sponsors free t’ai chi classes from 7:30 A.M. to 8:30 A.M. (212-221-7333). Meet at the fountain terrace at Bryant Park, but don’t plan on going barefoot: The class is held on bluestone slabs.
BYOB (bring your own birdie) to the badminton courts at the High School of Art and Design. Open courts begin at 7:15 P.M. ($25; 1072 Second Ave., at 56th St.; 646-271-3228).
Roller-skate at Chelsea Pier’s outdoor rink, from 1 P.M. to 5 p.m. Admission is free with a $19 skate rental (Pier 62, at 23rd St.; 212-336-6200).
There are synchronized swimming lessons at the Borough of Manhattan Community College from 2:30 P.M. to 5:30 P.M. ($490 for a ten-week course; 199 Chambers St., at the West Side Highway; 718-359-7743). Esoteric? Yes. Difficult? Not really.