Lousios river, also known in antiquity as Gortynius or Gortynios is a tributary of the Αlfeios river in western Arcadia, Peloponnese. It stretches from the village of Karytaina in the north to the village of Dimitsana and empties into Alfeios river. One of the river's sources is in the ancient town of Theisoa near the village of Karkalou, the other one further to the north, at the church of Agia Paraskevi near Kaloneri. These two streams meet up in Karkalou and form one river. Lousios continues its course and ends up after 25 kilometers in Alfeios River and flow into somewhere near Karytaina.
In ancient Gortyna there is the bridge of Kokkori and the section between this bridge and the Atsicholitiko bridge is called Ano Lousios. On the right bank as the river flows, are the ruins of ancient Gortyna and a little further down on the same bank, the Byzantine church of Agios Andreas. Until the 20th century the river’s power was harnessed by numerous watermills, whilst the cliffs above provided refuge to hermits and monks in caves and cliff-hugging monasteries, the latter of which is still inhabited. There are numerous monasteries, churches and hermitages around the river, evidence of the religious life that developed there in the past.
Lousios is an impetuous river and it contributed to the development of the wider area. The residents realized its power and took advantage of it by building tanneries, watermills, flour mills, distilleries and particularly gunpowder mills. All this activity made the area renowned for its art in in hydrodynamics. All this and much more can be seen at the unique Museum of Water Power in Dimitsana.
The river has been known since antiquity. Pausanias considered the river as one of the coldest in the then known world. According to mythology it was given this name because the newborn Zeus was bathed (Louzo=bathing) in its waters by the nymphs Theisoa, Neda and Agno. The river is ideal for rafting and kayaking. It is a particularly impetuous river and is certainly not recommended for beginners.