Hello,
Thanks for the greetings and compliments.
I still do NOT have a confirmation regarding the "мечеть во Владикавказе". But I have to leave to the business trip for a week and don't want to keep the forum uninformed for such a long time. The local people have received my query, but need some translation assistance. I will post their response here when received.
So, the following is just a theory, I don't have confirmation or disproval yet.
http://hdl.loc.gov/loc.pnp/prokc.21639The photo is from the album "Views in the Caucasus and Black Sea area, Russian Empire" at
http://hdl.loc.gov/loc.pnp/proka.0008a.39. The neighbouring photos from the same page are from the same region. It seemed so logical, that the photo was taken in the Caucasus. I started to search for mountain lakes, sea gulfs and even artificial water reservoirs close to the main roads, using Google Earth, Panoramio and Flickr. I looked in Russia, Georgia, Armenia, Azerbaijan, Turkey and Iran last summer. Then I just gave up, hoping that some brilliant analytical mind from the forum will identify the location soon.
Last week I got enlightened (I hope). Take a look at the following map of Northern Italy. PG had to pass the red circle during his expeditions:

The lake there is Garda (Gardasee, Lago di Garda). It took about an hour to find the following photo, taken at the Garda lake in the port of Malcesine, Italy. Ristorante Italia da Nikolas is currently running its business in the building. I post a fragment of the photo, where possible shooting points and direction are marked with yellow:

Original at:
http://static.panoramio.com/photos/original/5001109.jpgThen I opened a tourist information website of Malcesine at
http://www.malcesinepiu.it and saw a painting by Gustav Klimt "Malcesine am Gardasee" dated 1913. See the fragment, even one of the plants is depicted in front of the house:

Full high resolution image:
http://upload.wikimedia.org/wikipedia/commons/8/8b/Gustav_Klimt_042.jpgUnfortunately I did not find photos, taken from inside the restaurant. But I could determine, that there are lake and mountains on the horizon, if to look through the Western arch of the restaurant, the same direction PG could took his photo. Here is another photo, taken in front of the neighbouring house, direction West:

And one more indirect relationship, look at the dining room of hotel Sirena, less than 100 metres from the Ristorante. The arches look similar and there are metal bars under the ceiling:

Then I started to think about the opposite lakeside, visible on the horizon on the photo by PG. A little playing with contrast and brightness made the background a bit more clear, but the result is still quite fuzzy. At the opposite lakeside there is a village Campione. Using the Campione photo from Panoramio (
http://www.panoramio.com/photo/1193254) I tried to match some objects, but I am not sure that it is correct... PG's fragment is 100% below. Sorry for the size, but I didn't want to lose more details.

But if Malcesine people confirm, that the area marked below is visible from the PG shooting point through the Western arch of the Ristorante, then it is all correct...

Best regards,
J.