This is the monastery of Paulou situated at the foot of Mt. Athos. The tower near the beach is a defense tower probably from the Byzantine period. This photograph was taken a few years ago. The situation has changed since 2014 as we noticed when we walked there in december.
The tower is to be renovated, all the vegetation around the tower is removed, the riverbed is widened  and they are building terraces for agricultural purposes, maybe for growing grapes.
                                 
Are they renovating or rebuilding the tower? What used to be a small stream is now a large riverbed.
View from the path to Nea Skiti and Skiti Anna. Below first the dirt road to Paulou, then the dry riverbed and on the right from the tower, the new terraces.                       
View from Paulou towards the tower.
This is the oldest image of the tower I could find. This print is dated 1916.
Finally,  here you see the tower taken from the top of Mount Athos in 2013.
Herman Voogd