The path down to Thunder Hole is treacherous and it doesn't normally make a sound. The locals say that it takes a winter storm to make it "thunder" but that didn't stop the crowd from standing interminably in front of it. The only signage on Park Look Rd directs you to the gift shop and the path down to Thunder Hole is a little hard to find. Hint, it's BEYOND the gift shop on the other side of the road.
Cadillac Mountain is 1500 ft. high but has panoramic views of Mt. Desert Island. There's enough parking there - we only circled once.
Where there isn't enough parking is Jordan Pond. We had checked out the parking the day before and realized that we probably wouldn't be able to find a parking place. All 3 parking lots were full with cars circling looking for places.
Their web site is here and the TripAdvisor article is here.