Acadia National Park covers land across Mt Dessert Island as well as surrounding areas. A great place to start is the Hulls Cove Visitors Center. Here weeklong passes can be picked up for entrance to the park. If you have the National Park America the Beautiful Pass, be sure to bring it along as you will be able to use it for entrance into the park!
Cadillac Mountain offers gorgeous views of the ocean, lakes and mountains in and near Mount Desert Island. You can drive the main road, bike or hike one of several trails. Reservations are needed for vehicles, starting late in May but as this is a new system it would be a good idea to check dates as things go along.
From the waterfront leave early and pay attention to tides! When the tide goes out walk across the ocean floor to Bar Island in the harbor. Make sure to come back well before the tide comes in and don't park your car on the land bridge!!
Easy walking path includes gorgeous views of the Maine coast, Sand Beach, Thunder Hole, Otter Cliffs and often wildlife.
Multiple things to do can be accessed here. The Jesup Path Boardwalk is a slightly elevated boardwalk through woods and meadows that leads out of the Wild Gardens of Acadia, a garden of local plants and trees. Multiple hiking paths of various difficulties branch off from here. The Tarn path is the first that we took Nick on!
A favorite trail. More difficult than Ocean path but far from strenuous, with options for a "normal" climb up or a scramble up a rockslide. 360 degree views from the top including the Beehive (a distinctive mountain in the area) and Sand beach. We've even seen falcons playing at the top!
AKA Starfish beach. At low tide wade the water and see starfish!