Pokémopolis

If you were looking for the website, see Pokemopolis

Pokémopolis is an ancient civilization located right near Pallet Town. It made its only anime appearance in The Ancient Puzzle of Pokémopolis.

It was discovered by accident when Ash was battling Brock's Vulpix with his Pikachu. Although the two were the ones who uncovered it, an archaeologist named Eve took credit for finding it, and was honored for it.

Among the artifacts found in the ruins of Pokémopolis were several odd-shaped objects. As it turns out, those objects were ancient Poké Balls, and inside of them were a giant Alakazam and Gengar. The two were released, and it appeared they were going to have an epic battle right there near Pallet Town.

Luckily, a giant Jigglypuff was released as well. Using Sing, it made the other two giants fall into a deep sleep. Soon afterward, all three were put safely back into their ancient Poké Balls, with Eve promising to do more research on how they worked.