What do you know, there really was such a switch! The water is no longer flowing down into the room. You return and, having as much time as you need now, you can take the time to break down the small stone door. Eventually, it will crumble.

Break down that door.

Instead examine the mural.

Strict Mode (In Strict Mode, the game will not show you options that require a skill you do not have. In non-strict mode, these options will be greyed out but you can still cheat and access them. You can switch modes at any time.)