From the Mass Pike (I-90), take Exit 2 in Lee, Route 20 East. After getting onto Route 20, immediately turn right onto Route 102 (towards Stockbridge) and then immediately turn left onto Tyringham Road. Follow into Tyringham Center. At the small post office/library/town hall, turn right onto Jerusalem Road. Entrance and parking (16 cars) are on right.
One of the loveliest day trip destinations in the Berkshires, Cobble Mountain is a favorite of hikers and picnickers.