I've only been playing the game for three days so I haven't seen everything in game.
I have already looked this up and didn't find anything.
I think having bath tubs to relieve some stress (unhappyness) depending on how long you stay in the tub might be a decent idea and perhaps scented candles to boost the unhappyness heal rate.
Maybe being able to add salt to the bath water for some healing properties.
Tubs could be made out of wood or clay with metal.
Sorry I don't have very orginized thoughts.
