The closest thing to a Japanese-style onsen that I...

The closest thing to a Japanese-style onsen that I've found in California. It's a lovely, romantic spot - and the perfect third date (if you really like someone and they're not too squeamish about being naked). Go for a room with a hot tub, sauna and cold plunge - it's invigorating and offers a nice change between temperatures.

Also, if you can, get a massage - it's a nice relaxing experience after your already relaxing experience.