Gravenhurst is the southern gateway to Muskoka, but it is not just a sign on the highway north. The town sits on Lake Muskoka with a waterfront built around steamship cruises, wooden boats, summer theatre, and the birthplace of Dr Norman Bethune.
The best reason to stop is the lake heritage. Muskoka Steamships and Discovery Centre keeps the old resort era alive, including cruises on the RMS Segwun, while the wharf gives Gravenhurst a more active waterfront than many cottage-country towns.
Away from the docks, Bethune Memorial House adds a national historic site with a surprisingly international story, and the Gravenhurst Opera House keeps the old downtown useful after dark. It is a good one-day stop if you are already in Muskoka and want more than lake views.