This is Kings Landing the seat of power of Westeros from George R.R. Martin’s Game of Thrones created in Minecraft posted by Redditor pizzainacup. It took about 100 people a little over 4 months to create this, there are apparently 3000 unique buildings all with interiors. It can be accessed on www.westeroscraft.com.
It looks like they are planning on creating the entirety of Westeros and Essos, and are waiting on Minecraft’s Mod API so that they can release this as an open world RPG with quests and NPCs.