This is the entrance 0f Koutloumousiou seen from the courtyard. On the right side of the porch a pre christian, so called, Grave Stele is part of the wall. 
A stele is a stone or wooden slab, generally taller than it is wide, erected in the ancient world as a monument. Grave steles were often used for funerary or commemorative purposes (wikipedia). 
This Grave Stele is made in the mid-4th century Before Christ. The two figures are unmistakably women. The seated figure is the deceased. The standing woman, probably a servant, is holding a box and offering something to the deceased. This could be an piece of jewelry as it is in the beautiful Grave Stele of Hegeso, dated from ca. 410 – ca. 400 BCE.
The Grave Stele of Hegeso in the National Archaeological Museum in Athens. The jewelry, originally in the hand of the deceased, was painted but has now disappeared. 
Part of an article in a German magazine called Antike Welt by Ulrich Hübner about the Pre Christian object in Koutloumousiou. The writer is stating among other things that the Stele is probably placed in the wall a little before the 17th century. Originally the object is coming from Metochia (land elsewhere, owned by the monastery) outside Athos or from the eastern part of Greece.
Herman Voogd
There are a lot of pre-christian sites and assets to be found on Mt Athos. E.g., ruins / foundations on the way from Lavra to the Romanian Skete, on the Hill above Dafni, etc. I think even the waymark “cheira [χείρα]” near Sografou is of ancient origins.
Many of them are described in the Book of Smyrnakis.
Thanks very much for the images of the aqueduct and the insulators. I used some of them in posts 1983 and 1985.
Herman Voogd
A suggestion: I don’t now if it’s my network, but the posts with large images are loading pretty slow. Perhaps you might want to restrict posted images to HD or FHD sizes, and click on them links to the HiRes Image ?
You don’t happen to be on Mt Athos right now (14/3) ? If yes, pls contact me via private mail.
Thanks for the suggestions.
No, we are, at the moment, not on Mt Athos. We probably will be in september this year. We will vist the Mountain for sure in 2019. We will contact you when we know the exact dates. Thanks!
Bas Kamps, Wim Voogd, Herman Voogd