Northwood Golf Club in Monte Rio, California. Hands-down the best 9-hole course in the country, and I don't care that Golf Digest thinks Sweetens Cove in Tennessee is the best. I played that one, too, and it's not even close. This is one of the most unique courses in the world, situated among the redwoods, and is absolutely breathtaking. An Alister MacKenzie design.
Just played there yesterday for the first time in 25 years after playing it a few times in the '90s. Better than I remembered. The most fun you'll ever have playing golf, too. Bryson DeChambeau recently featured it on his YouTube channel and shot -2. My goal was to match that but alas, I shot +2 (good excuse - I'm a little rusty).
Link: DeChambeau YouTube video playing Northwood