A river that covers 220km starting from Pindos to flow into the Ionian Sea, while it crosses the prefectures of Trikala, Karditsa, Arta , Evrytania and Etoloakarnania. Acheloos, also known as Aspropotamos, along with its tributaries (the most important are Agrafiotis, Tavropos and Trikeriotis) constitute an important part of the ecosystem, enriching with their waters the artificial lakes of the area (artificial Lake Kremaston in Kastraki). The nature lovers can enjoy activities such as white-water rafting and canoe kayak with the help of organized schools.