Is that the Hearst mansion? I've heard it's worth checking out.
Ding ding ding yes that's the famous outdoor swimming pool at Hearst Castle.
The indoor swimming pool has stars on the bottom and the ceiling has fish painted on it.
They recently did a serious re-waterproofing of this outdoor pool, as there had been 80+ years of settlement and earthquake movement.
If you go there are three different tours and they are priced separately. I have never been on the third tour which covers the outbuildings gardens and stables, and the mile-long covered bower.
The first tour just covers the main floor of the castle, theater and pools. It is definitely worth taking before the other tours.
The 2nd tour takes you through the kitchens and pantries and up to the guest rooms and the towers and to the upstairs bedrooms.
Some of the work was revised in process, and you can see the scars where they chipped in and added another floor.
Some of the upstairs rooms are quite weird in different ways.