Filoli, a 654-acre country estate built in the early 1900s. It's located in Woodside, 30 miles south of San Francisco, and is considered an American castle. The original owner was William Bourn, whose wealth came primarily from the Empire gold mine in Grass Valley.
The sheer volume of blooming plants is almost beyond belief. I saw more pansies, one of my favorite flowers, than I have ever seen planted in one place. (All those purple flowers in the background above are pansies, and they were everywhere!) We went for an extensive walk around the grounds, then had lunch at the on-site cafe.