For some reason I want to say it’s a production still from “The night land: the movie.” 🙂
I’ve never read ‘The Night Land’ but Google tells me that it is from the same guy who wrote The House on the Borderlands and is about the earth in the far future when the sun has burned out. I will need to check it out!
that’s the one! post-apocalyptic and people live in massive pyramid-shaped cities.