Where do you catch mu2 on pokemon diamond?

In Pokémon Diamond, you can catch Mewtwo in the Cerulean Cave, specifically in the area known as the "Cave of Origin." However, you must first complete the main storyline and become the Pokémon Champion. After that, you can access the cave, which is located near Cerulean City, and navigate through it to find Mewtwo at the bottom. Be prepared, as Mewtwo is a level 70 Pokémon and can be challenging to catch!