Located in the Worthington State Forest (just below the Delaware Water Gap), the hike to the top of Mount Tammany is one of the most rewarding hikes you could ever take. The trail has one of the largest vertical differentials in New Jersey; it rises 1200 feet in just more then 1 mile. Because of this, there are sections you will have to climb, or at least crawl up. However, the view is worth it. Sitting on an almost-overhang on the top of the Delaware Water Gap and enjoying the view is a great experience.
Though there are multiple trails to get to the peak, you might want to consider parking in the Dunnfield parking lot (off Rt80. See the map for info.