I recently had the pleasure of staying at the 4 Seasons Westlake Village as a guest during a work seminar my boyfriend attended. While he was busy all day, I got to take advantage of the facilities and location. While the surrounding area is a bit deserty-dry and in the "middle of nowhere" within a 20 minute drive are the waves of Malibu, and if you're adept at avoiding traffic, a trip down into LA is easy as well.
The hotel itself is lovely, understated Californian architecture from the outside (a modern version of the Craftsman period, perhaps?) and the inside is lovely. Free services and amenities abound, from complimentary hot towels and tea at random sconces within the halls, to a fully outfitted gym. The rooms are lovely, the views are decent, we looked out over a gorgeous garden with a manmade waterfall.
Perhaps the best part of this hotel is the SPA, which is 18+, as is their outdoor "serenity" pool. The complimentary spa features offer multi-headed showers, hot tubs, dry saunas, steam rooms, locker facilities, and dry resting beds in gender-specific areas.
I LOVED my stay here, and will eagerly go back next year. I've been converted to a 4 Seasons fan.