Lousios is a small river of Arcadia, 23 km long, which stems from ancient Theisoa and from the ridge of the mountains of Lagadia. It passes west and close of Dimitsana, and flows into Alphios River, 2.5 km northwest of Karytaina.
The water is quite violent, forming waterfalls and maintains the same temperature throughout the year.
Its route is passing through willow, poplar and osier trees. The gorge has a wild beauty and rich vegetation that blends seamlessly with the rocky landscape. West of Karkalou, there is a great variety of birds and reptiles. In its waters there are not many fish as opposed to the number of crabs. The climate of the gorge still favors the bats that have shelter in caves and in abandoned monastery buildings.

The riparian area of Lousios, at the most part, is steep with sharp rocks, making it impossible to pass through them.
The gorge is of natural beauty and since 1997 has declared as an archaeological site and is protected by the Ministry of Culture. The flora and the fauna are rich and coexist harmoniously.

According to the ancient mythology, to which owes its name, but also and from references of Pausanias, the Neda, Agno and Theisoa Nymphs bathed Zeus - in secret from Saturn - in the source of the River (Sources of Immortals), when he was born. Pausanias also considered that Lousios was the coldest river in the known world.
Later, it was renamed to Gortynios, taking its name from the ancient Gortynia.

The Lousios's gorge is also known as the Mount Athos of Peloponnese, because of the developed monastic life, especially in the era of the Turkish occupation. Many factors had their role in it, like peace, quiet and religious sentiment of the people. Hermitages had been created, monasteries, churches and chapels. Most famous are the monasteries of Philosopher, Aimialon and others.

In the gorge, there are many sources of abundant waters that led to the development of a kind of a small industry, from the 16th century, based on the Water Power. Mills were built for the grinding of the cereals, mills as tanneries for the processing of leather, gunpowder mills known also as "mparoutomili", water mills for the treatment of clothes, water-saws for cutting logs, etc.
In the same area there were lime kilns, tile workshops, olive-mills and distilleries for the production of raki.
Today, there operates an open-air Water Power Museum.

The coupling between the villages, settlements, monasteries and watermills was mainly done by trails and stone bridges. On the path to Lousios there are sixteen stone arched bridges.

For the tourist development of the region, the old trails, in the gorge, have been preserved and been restored in order to facilitate the crossing of the hikers, and the access to sites. The area attracts today many visitors and walkers. The routes through the regenerated paths end up to ancient Gortyna, while the start is at Dimitsana, St. John, the Baptist Monastery, Elliniko and Ancient Gortyna.

Lusios River, apart from walking, is also suitable for other activities. At the stone bridge of Atsicholos, near Karytaina, descents of rafting, kayak, trekking canyoning and more other are organized by companies of alternative tourism. Other descents reach its junction to Alphios, and others cross Alphios, attracting many fans of this activity for memorable experiences in a beautiful and virgin nature.

In a distance of 5 km from Karytaina is Lousios's bridge, which is the starting point for most rafting trips, etc., for a distance of 4 km until it meets Alphios River. The trail continues for another 3 km with a total duration of one hour, a unique experience and adventure.
The end of the journey takes place at the bridge of "Cuckoo" in Alphios.
The bridge has a height of 34 meters, 4 meters wide and 25 meters long and boasts for its perfect construction although its inaccessible location. It is built in 1880 with a government grant in order to connect Gortinia and Olympia. It is a wonderful work of the master builder Anthony Katsianou from Lagadia.

Waterfall of Vrontos
In a short distance (5-10 minute of walking) from the end of the path, you can see the waterfall created by the waters of Vrontos sources, which are falling from a height of 17 meters, surrounded by plane and broadleaf trees, before reaching to Alphios river, which, in mythology, was the beloved river of Zeus and brother river of the Ganges River in India.