Where Steven at the lilycove city?

In Pokémon Emerald, Steven Stone can be found in Lilycove City after you defeat the Elite Four and become the Champion. He is located in the Lilycove Museum, where he can be found on the top floor. Players can challenge him to a battle or interact with him to obtain the HM for Waterfall. Additionally, he plays a role in the storyline involving the Legendary Pokémon Rayquaza.