Step up one and all, and try to dodge Donkey Kong's falling barrels in the classic Atari 2600 game. Except each barrel takes fifteen hours to fall one level down. And the Atari 2600 is made of soil and stone in a mythical realm where everything is made of organic blocks. Using virtual textured cubes to store bytes of information, YouTuber SethBling built a fully functioning (albeit very slow) emulator of an Atari 2600 inside of the game Minecraft. SethBling is a veritable Minecraft wizard, who also once built working BASIC programming inside the game. It's a virtual world built inside of a larger virtual world.
The Atari 2600 he created is essentially a field of soil with a giant floating screen on one end, and some giant walls made of stone and soil on the other. The field contains the memory used by a 6502 processor (the same that ran the Atari 2600) and the gravelly walls are the 4 kilobyte ROM cartridges that store the software for the games. Dirt blocks are 0s, and stone blocks are 1s. SethBling built three cartridges so you can power up Donkey Kong, Space Invaders, or the horrible version of Pac-Man that made everyone not want to play video games for awhile. Unfortunately the Atari 2600 ran at about 60 frames per second, and the Minecraft Atari 2600 emulator runs at 60 frames every four hours. So, yeah. It's glacially slow. But it's the creative feat that matters.