It's a work in progress, but someone on Reddit is making the entire Kanto region in Minecraft.
Reddit user u/thisisminenow posted a screenshot of their progress so far. It looks like they've got a pretty hefty amount of work left, but there's definitely the bones of a properly laid-out Kanto there. Check it out below.
As you can see, it's the FireRed/LeafGreen version of Kanto. The most filled-out part of the map right now is the southernmost area, where you can clearly see some distinctive landmarks from the game. Cinnabar Island is down the bottom, with Pokemon Mansion, Blaine's Gym, the fossil restoration centre, and a Pokemon Centre/PokeMart combination on the bottom right of the island.
If you continue east from here, you'll see the Seafoam Islands, home to Legendary Ice-type Articuno. A bit further east and you can swing a left into a more northerly trajectory, at which point you'll reach Fuchsia City. The buildings on the same plot as the Gym seem to be constructed, but the Safari Zone up north hasn't been built yet.
If you were to start at Pallet Town and proceed as if you were actually playing Pokemon, though, you wouldn't be allowed to hit Cinnabar yet. Instead, you'd go north until you reached the already-built Viridian City. The whole route through Viridian Forest to Pewter City is visible in the aerial photo too, as is the path east to Mt Moon.
There's a decent amount of the map left to build, but this looks like a very promising start. I'm excited to see how Victory Road turns out, and to check out a Minecraft version of the iconic Indigo Plateau.
In related news, Minecraft is getting its first major update in quite some time later this week. In terms of other Minecraft constructions, one player spent two years building Chernobyl in-game.