#20. When I first saw the boulders lining the planted areas in the Tribeca section of the Hudson River Park, I thought they’d be fun for kids to scramble over. But then, as I got interested in running—and bored with running—I began running on anything in my way, such as park benches and curbs. One day, I saw someone running on the boulders, and I haven’t been able to resist them ever since. Try it: It’s a blast (and a good workout).