This image could be practicle if your are visiting a church on Athos. Where you see Porch (at the entrance) in the Athos churches you will find the Exo-narthex, with in most churches beautiful frescos and stained glas windows. As a non-orthodox visitor in most cases during services you will not get further then the Narthex. After the service you sometimes will be invited to go to the Nave accompanied ofcourse by a father. We got, for instance, a very nice tour in the monastery of Vatopedi where they even showed us the holy relics in the Nave near the Templon. The Sanctuary is a no go area, I think not only, for non-orthodox but for every pelgrim. I found this picture on this blog.
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In 1980 the Sanctuary of Vatopediou was NOT a no-go area for us, because we were invited to come through the door of the Iconostasis and see the relics (f.e. the Girdle of Maria).!!! We were allowed to go there because we were Protestant………….(?!).
The sanctuary can only be entered with the blessing of the priest (or hegoumen). Usually this privilege is only granted to male Orthodox Christians, but be sure that they let in cleaning ladies from time to time 😉