A spin around the park on a bike makes me feel good. One lap is about 6.13 miles. I've trained here for longer rides (including this London to Paris ride on a track bike that was 86 miles one day, rest on the second day, and 136 miles on the third day). I've sat there on a Sunday afternoon and have done as many as 10 laps (with rests in between). I switch in-between my carbon road bike and my steel track bike.
The best part of the new Whitney Museum is the view in all directions from the terrace - and also from the staircase facing West. I'm afraid it upstages the Art.
Erie Basin is a really wonderful little shop full of old, creepy and beautiful things, such as Victorian mourning jewelry (some with hair in it), Freemason masks from the 1900's, tiny children's rings from the 1700's, and all kinds of other treasures. It is really as much a museum as it is a store, and all of the items have a haunting and unique aura.
The oldest still-operating restaurant in New York City, still in the family of the original founders. At Christmastime, it's decorated to the nines. Go with a big group: portions are large and the wine flows liberally. Look for the little buttons on the walls: in the old days, the mafia would hang out in the back room, and if diners saw the cops come in, they'd press the buttons so the mafia guys could run out the back.