Silent Hill 2: need help at the Lakeview Hotel!

[Ruby Moon]

Can't complete the Lakeview Hotel puzzle of the three music boxes. I need to find the last music box, but I can't! I have the Snow White and the Cinderella ones.
Where is the last one?

[Uchiha Sasuke]

Did you go into the weight elevator yet.You have to go down the elevator and pick up the last box

[Pu the Owl]

I think you can find the Mermaid music box, if I'm not wrong, in the fountain of the hotel.