Round in form and three miles across, with a large prominent island in its north end, most of Isabella's 1516 acres are less than 15' deep and its greatest depth but 18'.
Rocky shoals are common in the center of the lake.
Isabella is a part of the extensive Kawishiwi River watershed. At the east end of the lake is the mouth of the Perent River, a little traveled and often challenging wilderness river, running down from Perent Lake . The forest around Isabella dates largely from the big Lake Insula fire of 1864, with significant remnants surviving from the earlier 1824 burn. The Independence Day windstorms of 1999 did no significant damage in the Isabella area. Campsites Isabella supports a dozen established campsites.