From Route 128 North or South-bound, take Exit 26, Weston/Waltham. Leave the circle (over 128) heading east towards Waltham.  After the traffic light, take a hard left immediately after the gas station.  Sign says "to Rt. 117".  Go down to the traffic signal and head west (left) on Rte. 117.  Go 3 1/2 miles to Tower Road.  (You will see the "Entering Lincoln" sign after 3 miles.)  Take a left on Tower Road, cross railroad tracks (slowly), then take your second right which is Stonehedge. The road winds (bear left at the fork) for about a half mile to a dead end.  Just before the end, look on the right for a big mailbox with the name KNOWLTON.  Drive up the driveway and park to one side.

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Special alternate route if you're coming from the north shore area:
From Route 128 Southbound, take Exit 30B, Route 2A, Hanscom A.F.B. and Concord.  Proceed 1.8 miles west on 2A past Hanscom A.F.B. entrance and turn left on Bedford Road.  After 0.8 miles, proceed straight through the Route 2 traffic signal. Continue for another 1.1 miles to a STOP sign at a 5-way intersection. Proceed straight through the intersection on what's now Lincoln Road. Cross railroad tracks after 1.5 miles; go another 0.1 mile and turn left on Codman Road. After 0.4 mile and a STOP sign, bear left onto Route 117 (east). After 0.3 mile cross railroad tracks again, and after another 0.3 mile turn right on Tower Road.  Proceed 0.2 mile and cross railroad tracks a third time; another 0.2 mile and turn right on Stonehedge Road. (This is the second right after turning onto Tower Road.)  Stonehedge winds (bear left at the fork) for about a half mile to a dead end.  Just before the end, look on the right for a big mailbox with the name KNOWLTON. Drive up the driveway; park to one side.