How do you get to the cave in Sootopolis City in Alpha Sapphire?

To reach the cave in Sootopolis City in Pokémon Alpha Sapphire, first enter the city and head towards the center where the large body of water is located. Use Surf to navigate across the water to the entrance of the cave, which is situated on the western side of the city. Once you reach the cave entrance, you can explore it for items and Pokémon encounters.