Something unusual in the back garden. And identify this castle?

I live in a street in North London that is plagued in the mornings by parents dropping off their little darlings at one of the numerous local schools. I used to walk or ride a bike to school - and I can't see why the blighters can't do that today - of course if you were to ask the parents that question the response would be that there was too much traffic for their children to walk safely to school (of course - it never occurs to them that they are the traffic at that time of the morning!).

Anyway, every so often on a Friday or Saturday night we sometimes get the odd drunk toss his empty beer bottle onto our front lawn. The following morning, I sigh, and pick them up. After all, I work in the drinks industry and I can hardly complain if someone enjoys the product a bit too much (although when they've been drinking Dos Equus I have to question their taste in beer). Anyway, I'm sure some of  you have had the same experience (or, - shame on you - have dumped an empty in someone's front garden yourself).

So, about a year ago my wife and I paid a quick visit to Beirut. While we there we visited a cousin, Sally, at her family home up in the hills above the city - they had built a beautiful house and garden by a steep hillside (practically a cliff), safe in the belief that nobody would be nuts enough to build there - and guess what? Over the next thirty years the house became surrounded by the usual sprawl of houses and apartment blocks (Beirut has no planning laws as far as I can tell).

Sally's Dad is pretty old and I said I'd help clear up the yard, which was very overgrown. And while we found some empties (the local brew, Almaza, is actually quite nice) what brought me up short was to find something Russian in the back garden - and I'm not talking empty bottles of Baltika:

So this is it a few days later after a clean up (don't ask where the clip came from). We think it was tossed over the garden wall by some fleeing militiamen during the war but at the same time seems to be missing some parts that I'd expect to see if it had been thrown aside in a panic.

And here am I the militiaman!

The other thing they had that caught my eye was a painting in the library:

Now this was a painting that Sally's Dad had picked up when he was working in London (he was a surgeon before he retired) but he knew nothing about it. It looks to me like a castle built by Edward I to secure the Welsh conquest but I don't recognise the castle. Of course it could be a stylised depiction, I suppose. If anyone has any suggestions for it being an actual place, please let me know.