When I first lived in Jeddah we were in "the Northrop Compound" (actually six villas behind a high steel gate) "behind Al-Mokhtar's" (... quite a few people will remember that fine
emporium I should imagine)!
... and (for others who may be tuning in), everyone has a "P.O. Box", and the "post code" actually refers to the post office! That is, unless things have changed since the five or so years it's been since I came out of the desert.

P.O. Box 123
Riyadh 11411
... with the 11411 being the (main) post office in Riyadh. And er, no ... there aren't 11,411 post offices in Riyadh. Not yet, anyway.
Odd, you may say? What use is that? Well, let's just say that if it was
too logical it just wouldn't belong. And the
really interesting thing is that same system prevails all across the Kingdom. That is, in every little desert town that boasts a post office (usually the size of a typical corner shop in England)!
On the other hand, the Post Code system
developed in the UK is that most rare of examples, something that the government(s) (of the day) actually got right!
Remember
"remember to use the postcode"? And now Neil is reminding us all over again!