Scotty's castle is a castle in the middle of the desert!. A magnate decided to build this mansion, which has twenty rooms spreads out over 3658 square meters, for dry weather was good for his health. It is a Spanish hacienda-style palace. There is a tour every 30 or 60 minutes from 9 to 17h. I've only seen the Scotty Castle from the outside. If you arrive late you can visit the showroom for free.
If your route is from Las Vegas to Los Angeles or Yosemite or the reverse, in order to see Scotty Castle, you'll have to divert to the northwest of the 190 to the 267. If you are doing the route and not doing very well on time, perhaps it is not worthwhile because you have to go back to retake the 190 or 178. If you're not limited on time, then drive the extra 15 miles.