While staying in Ogunquit we decided to take the drive to the top of the mountain. It's about 20 mins from town. We fit it in after the beach one day before dinner.
No fee is charged for admission. At the top of the mountain there is an old ski lodge, and the supporting structures of old ski lifts. The place isn't very well maintained and there are several radio antennas and cell towers. Not what I expected.
However...the views of the presidential range and the coast were well worth the drive. We did not stay long. Maybe a half hour. There are picnic tables at the top... and there are hiking trails. You could park at the bottom and hike up.