Riso Naruohama is a large pool and water park. There are many large indoor pools with a slide. Outside, there is a large pool, a large hot spring pool, and some more slides plus a grassy area with a view of Osaka Bay.
Besides the small, but hot spring water filled, washing and bathing areas, everything is mixed bathing with bathing suits as a requirement. Bathing suits are for sale and rent in the building or you can bring one yourself. They have a bunch of snack carts but everyone sneaks in their own snacks and drinks. I always stash a few beers in my bag for a day here.
Riso is a wonderful place to spend the day with your family or friends.
Discounted admission is available if you come after 5pm. Coupons for Riso are everywhere. I’ve never gone in paying the normal price.
On busy days in the summer the parking lot might fill up quickly. Check the twitter status updates on their homepage for more information.
The outdoor pools are only open in the summer.