Ile Rousseau is the small island where Lake Geneva narrows into the Rhone, named for Geneva-born philosopher Jean-Jacques Rousseau. A statue of Rousseau stands among the trees, and the bridges around the island give good views back toward the lake and the old city.
It is a short pause, not a destination for an afternoon. Work it into a lakeside walk between the Jardin Anglais, the Mont-Blanc bridge, and the Paquis waterfront.