Moosehead Lake / Greenville (35 miles north) — Maine's largest lake, and one of the great wilderness lakes of the Northeast. Greenville is the main town on the southern shore, with seaplanes, moose-watching tours, and access to the lake for fishing, kayaking, and boating. Moose sightings are genuinely common on the drive up. Worth a full day at minimum.
Baxter State Park / Mount Katahdin (about 90 minutes north) — the highest peak in Maine and the northern terminus of the Appalachian Trail. Baxter is a serious wilderness park with strict access rules and no services inside. Katahdin itself is a full day's hike and requires an early start. Book your vehicle permit well in advance, especially in summer.
Sebec Lake (about 10 miles east) — a quieter alternative to Moosehead, with good swimming, boating, and fishing in a less visited setting. The lake has a handful of access points and small camps around its shores. Good for a half-day trip if you want water without the drive north.
Bangor (about 2 hours south) — the nearest real city, and a useful day trip if you need supplies, a proper meal, or a break from the woods. Bangor is Stephen King's hometown and leans into it; the downtown has some good independent bookshops, restaurants, and the kind of infrastructure you will not find further north. Bangor International Airport is here if you need to fly in or out.