Hiking doesn't just mean trekking to the top of the Empire State Building or to your seventh floor walkup. There are some great hiking options right in Manhattan, and if you're willing to go outside the city a bit, there are even more.
For the ultimate stair workout, Fort Tryon in uptown Manhattan has some epic rock stairs and weirdly technical paths-it's also right near Inwood Hills Park, which has some excellent technical trails and singletrack.
But if you're looking for a full day-long hike (or overnight adventure), you'll want to go north to Bear Mountain and Harriman State Park where you can find some amazing hiking trails, gorgeous views of the city and the Hudson River (from the highest point at Bear Mountain) and even hop onto the legendary hiker paradise of the Appalachian Trail. There are camping options available at Harriman if you want to make a weekend out of it, and the trails range from beginner-friendly to wickedly technical.