The holy church of Agios Stefanos is located outside of Kastri, near Argoulio, in the location “Koukoumos”. It is a one-room building from the 14th century.
The Church is decorated with frescoes that date back to 1391 according to an inscription that exists in the church. Among the performances, the Melismus in the niche of the Sanctuary and the stoning of St. Stephen that covers part of the wall on the right stand out, while in other places we see the Deposition, the Resurrection, the Epitaph Lament, the Baptism, the Dance of the Women, the Dance of the Prophets, with St. Stephen standing out first. The depiction of God blessing the First Martyr is one of the rarest. Also at the door of the temple there is the representation of Hell, the sea and the earth that gives the dead at the Second Coming. Particular elements in this temple are the built-in plaques located above the entrance door.