This hike starts in Adams, Mass on Thiel Road. You can drive the road as far as you can until you reach a barrier. There is plenty of room to park off the road on both sides. You will walk he road for 0.5 miles until you meet the foot trail, marked as Thunderbolt.

The Thunderbolt Ski trail was originally built in 1934 and rerouted in 1937. It was the site of Massachusetts State Downhill, Eastern Downhill Championship, and various local time trials and trophy races throughout the 1930's and 40's.

Climbing the eastern side of the mountain this is the steepest trail up Mount Greylock (Massachusetts high point 3491 feet). At about the 1 mile mark from your car the trail becomes considerably steep and heads toward the summit ridge. At approximately 1.9 miles you reach the summit ridge known as Hadley Lookout with beautiful views of the town of Adams below. The last 0.5 mile stretch is along the Appalachian trail. The trail will pass a small warning hut shelter.

The summit features A Veterans War Memorial Tower and Bascom Lodge featuring overnight accommodations and meals May - October. There is a road to the summit as well opened seasonally.