In my archive I found this picture taken in 1997. It might be the “lake” HV mentiones in his blog nr 781:
Wim, 2/5
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Athos – Agios Oros
Athos - Agios Oros 
You have to be right. Do you remember the chapel or is that a new building?
In the background of your photo: the ruins of the Athonite Academy only visible if you enlarge.