The Eel River runs along the western edge of Fortuna, broad and gravelly through its lower reaches, and is one of the largest rivers in California. In summer it slows to a series of pools and runs that the locals fish for steelhead and chinook salmon; in winter it can swell with rain to spectacular widths and occasionally floods the bottomland farms.
The river bar at Fortuna is a casual swimming spot in July and August, with bonfires after dark in season. The gravel road along its eastern bank is good for a slow drive or a bike ride. Pacific Lumber Company once ran log drives down this water; the timber industry's footprint is gone, but the broad valley it shaped is still the most distinctive piece of geography around the town.