A reader sent this over today, and at first I thought it was a mod. Nope, turns out it's a glitch in GTA V, one which sucks pretty much all the textures and detail out of Los Santos, leaving one of the best-looking games on the planet looking more like something you'd find on an N64.
There are a few videos on YouTube showcasing the bug, dating from December 2014 to yesterday, all from the PS4 version and all with similar joke titles, variations on GRAND THEFT AUTO V FOR THE N64. Every video is taken at the exact same point in a GTA Online mission, given how there's an identical briefing text in each video, so I guess that's where the rogue code is hiding.
It looks like a problem with the game failing to add models and textures from long distances as you travel. These houses and hills should be getting more detail as you get closer, but as you can see, they're getting nothing of the sort.
Some modern games have to work hard to look this bad. Nice to see Grand Theft Auto V can manage without the help of mods.