Pokémopolis

It was discovered by accident when Ash was battling Brock's Vulpix with his Pikachu. Jigglypuff landed between the two Pokémon as they were preparing to attack each other during a training battle and were forced to deflect their attacks. 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 on the spot.

Luckily, a giant Jigglypuff—presumed to be the ancient defender of Pokémopolis—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. Eve said she would continue efforts to uncover how the ancient structures operated.

The stone tablet

A stone tablet discovered nearby contains an ancient script that was deciphered by Eve.

Beware the two great powers of destruction,

the shadow of the dark device will grapple with the prisoner of the unearthly urn.

The sacred city will be no more as day is swallowed up by night.

Darker still for you when they return to lay waste to the world,

but no human knows the secret to soothe the powers and guide them back to the shadow world.

The recurring stone tablet

• Pokémopolis is one of two known ancient civilizations in Kanto. The other is Pokélantis which happens to be in the same area.
• A stone tablet very similar to the one that Eve deciphers appears in the episode A Ruin with a View. It shows up in the possession of Professor Alden, who learns from it the way to get into the stone chamber of the Oldale Ruins.
• The name Pokémopolis could be a portmanteau of the words "Pokémon" and "Acropolis", an ancient Greek term for a city on elevated ground.