Arachthos is the 8th largest river in Greece with a total length of 135 km. Its source is in northern Pindos near the town of Metsovo, hence its upper course is known as Metsovitikos. It flows towards southwest through gorges, enters the small valley that is formed between Lakmos and Mitsikeli mountains and from there it flows east of Ioannina, where it receives the waters of Dipotamos river. From this point on it takes the name Arachthos and passing through the enchanting Tzoumerka it creates enchanting landscapes. After receiving the waters of two more rivers, the Kalarrytikos and the Sarandaporos, it continues through the lowlands, south of Arta and empties into the Amvrakikos Gulf near Alyki, having crossed a part of Ioannina prefecture and the whole prefecture of Arta.
Arachthos, along with Louros river, create four lagoons, the Lagarou lagoon (the largest of the Amvrakikos Gulf), located east of the hill of Salaora and the three-part lagoon complex of Rodia, Tsoukalio and Avlikora, which is located west of the hill. The four lagoons compose one of the most important wetlands in Greece, having been included in the ecological protection network program "NATURE 2000".
Stravon mentions Arachthos with the name Arathon, and Lycophron with the name Araiton. In an ancient inscription in Corfu it is written as Arachthos. According to local tradition of Epirus, the river is also known as the "River of Arta" , due to the legendary and much-sung bridge of the city, which according to tradition, in order to be built, the master builder's wife, had to be sacrificed.
The river is rich in fish fauna that includes wild trout, dewdrops and mustaches. Also in Arachthos are found populations of otter or European otter. Its waters are also suitable for water sports, such as rafting and canoe kayaking. Rafting in Arachthos is an easy and beautiful descent, ideal for beginners with some light waves, repeated turns and 2nd to 3rd-degree crossings.