Agios Sostis is located at the borders of the prefectures of Arcadia, Ilia and Messinia and it is built at an altitude of 850 m on the bridge and 900 m at the upper village. The story of Agios Sostis is intertwined with the historical site of Gorena - which archaeologists say is the Parassiac town of Lycoa - located on the northwestern side of Mount Lycaeus, as well as with the settlement of Tsouraki (Turkish name for the small hut).
The village is known for the church of Saint John. In the place where the church is today, there was once a Byzantine monastery, which was destroyed by the Franks in 1300. Following a vision that John Constantopoulos, who came from Agios Sostis, had, excavations began and 60 cells, a golden tweezer, a chalice, and a cross were found. The neighbouring villages assisted in the erection of the present church and established the traditional fair which takes place every year on the 29th of August with a large influx of people coming from the surrounding villages. The village was named after the saint's intervention.
Another modernistic historical element of the village is the unfinished Byzantine church of the Holy Trinity in the centre of the village.
Its construction began with money sent by immigrants from America but remained unfinished when funding ceased after the 1929 US crisis.
Evidence of the extremely harsh living conditions and the vision for a better life is the fact that many young people from 1900 - 1930 emigrated to America, which had as a result 4 of them to be found in the Titanic and were the only Greeks that lost their lives in the famous shipwreck. These were:
Liberopoulos K. Panagiotis 30 years old
Chronopoulos M. Apostle of 26 years old
Chronopoulos M. Dimitrios 18 years old
Katavelos Vasileios 19 years old