When was the right wing added?
1744 drawing by Barsky.
1853 one of the first photographs by Ernest de Caranza and Emile Charles Labbé.
1867 1872 by Russian monks of the Panteleimonos monastery.
1883 by Athelstan Riley
1906 postcard
Early 20th century, unknown photographer. Simonos Petras was rebuild in 1893 – 1902. Probably the right wing was added in those years.
1926 – 1930 by Robert Byron
21st century by Wim Voogd
Voor Gerard Koolschijn
Herman Voogd
Athos - Agios Oros 
Many thanks for your flashing reaction, Herman!
Has been built roughly 110 years ago, after the last big fire