The Acheron is the river of mythology — one of the five rivers of the ancient Greek underworld — and the one whose mouth lies at Ammoudia. The lower stretch is broad and slow, flanked by tall reeds and small fishing boats; further inland, in the foothills around the village of Glyki, the water becomes ice-cold and clear and runs between high cliffs.
Small boats from the Ammoudia harbour run hour-long trips up the navigable lower river through the protected wetland; the price is modest. For the upstream gorge you need a car: the Glyki section is roughly 35 minutes inland, with parking, restaurants, and pebbly paths along the banks for wading. The water is shockingly cold even in August.