The best day trip from Sudbury is Killarney Provincial Park, about 90 km southwest. The white quartzite ridges of the La Cloche Mountains were a favourite painting subject for the Group of Seven, and the park's lakes — Topaz, OSA, and Killarney itself — are some of the most beautiful canoe waters in Ontario.
Manitoulin Island, the world's largest freshwater island, lies south via Espanola and the small swing bridge at Little Current — about a 2-hour drive. The drive itself is worth it, through the rocky shield country and across the bridge with the boats backed up either side.
North Bay, on Lake Nipissing two hours east, makes a longer day out if you want a contrasting Northern Ontario town.
For a shorter trip, the French River — birthplace of the voyageur fur-trade route — is an hour south and offers boat tours and short trails along the gorge.