Mount Prospect, Mount Williams, and Mount Greylock Loop via Appalachian Trail

If you're in great shape, this is a fantastic way to experience the best of Mt. Greylock State Park. It makes for either a really long, strenuous day-hike, or a moderate overnighter (note: the main campground requires reservations May through October, so check Mass.gov if you intend to do this). The loop starts at the Pattison Rd. crossing of the AT, ascends the northern spine of Mount Prospect 1,500 feet in just under 2 miles, continues to Mt. Williams, Mt. Fitch and the highest point in the state, Mt. Greylock, before plunging south on the AT to the Hopper Trail and down to the Money Brook. You'll descend 2,200 feet into what's know as "The Hopper," passing through the developed campground roughly halfway. You'll cross the Money Brook before finally ascending 1,400 feet in just over a mile up the gnarly, southern spine of Mt. Prospect, and trekking across its top en route to the return via AT north and the finish. After Mt. Williams and Mt. Fitch, before the final push up to Greylock, there's an interesting side-route called "Robinson's Point" where you can get a great view of most of Mt. Prospect from across the Money Brook ravine. It accounts for a little less than a mile of the total distance, but it's a neat trip through dense-growth forest, and the view from the point really sets the tone for the latter stage of this hike. Both ascents of Mount Prospect are challenging, and the southern area is definitely bear-country, so use caution and be prepared to turn back. The Money Brook trail to the AT via Wilbur's Clearing is a fine alternative to the southern section of the Mt. Prospect trail, and less strenuous, though far less rewarding.