Hike to Mount Greylock and back:
3491 feet high (2200 feet up)
4 miles 3 hours (moderate)
via Thunderbolt Trail
Just hiking up:
2 miles 1 3/4 hours
Hike List: New England 50 Finest
Guide: The Thunderbolt Trail
Website: Mount Greylock State Reservation
Website: AllTrails
Wikipedia: Mount Greylock