Are you referring to Method of Loci? I've experimented with it a bit. For a while I would do daily mental walk-throughs of the apartment I grew up in and I practiced visualizing symbols for the 10 digits. After a few months I was able to successfully remember some pretty long numbers. Ironically, I don't remember how long they were. It wasn't that useful though. It took me a really long time to "store" numbers; longer than it would to just write it down. I didn't have a system for storing anything besides digits. Worst of all, the "memory space" was limited to the size of my old apartment. I was able to increase the space by adding detail to rooms but it was never enough to be practical for anything besides trivia. Strangely the repeated "walk-throughs" ended up bringing back memories of smells and textures that I hadn't thought about in decades

I think I'm much better at remembering and imaging things that can be easily articulated. I recognize my wife with no problem but I can't really summon a good mental image of her. We have a photo of the night we met. I can visualize details of the clothing and jewelry she was wearing but when I "look" at the image in my mind I can't really see her face. It's hard to describe. Almost like there's an image with a tag that says "link to wife's face here" without actually loading it. When I really concentrate on it I can wither get a really blurry image of her face, a really zoomed in image, or a sort of "line art" version of her face. I don't have real prosopagnosia. I can recognize faces, it just takes many more exposures than it does for most people.