Kalarrytikos is the most important tributary of Arachthos and originates from the mountains of Kakarditsa and Peristeri. It is a rushing river that follows a route through wild gorges, with waterfalls and stone bridges. Arriving at the Gogkou bridge, it calms down but then rushes again, crossing one of the most beautiful gorges in the country, the Gorge of Kalarrytikos before it flows into Arachthos.
Three streams are what create the river, the stream of Chrousia that starts from Peristeri above Syrrako and Kalarrytes, the stream Karlimbou (Gate of Paradise) that has its sources in Kakarditsa and the stream Matsoukiotiko. In its course it also receives the waters of the Melissourgiotiko stream.
It is one of the most beautiful rivers in Greece ideal for river sports such as rafting and kayaking. Difficult route rafting ideal for adventurous and experienced rafters. Kalarrytikos is boasting some of the most difficult route passages graded third and fourth level. It passes through an alpine wild landscape, down a narrow canyon with wavy rapids, many springs and waterfalls as well as the beautiful Arachthos Gorge.