It was a very good day for the trip. The weather was warm and sunny, but not too warm. (It was even a little chilly in the breeze.) I drove to the top without incident--- there were actually fewer bikers than I expected on the road. Despite my fear of heights I enjoy the drive.
From the top of Mt. Diablo I had no difficulty at all seeing the Golden Gate Bridge and the San Francisco skyline. I'm never sure whether I can actually see the Sierras, or just a cloud formation off on the eastern horizon. I could see a new wind farm to the north of the Sacramento River, and had good views of most of the Bay Area bridges. (On a previous trip to Mt. Diablo the top was buzzed by a Rutan-designed airplane--- a VariEze?---, but nothing so dramatic occurred this trip.)
I went for a short hike on the path around the summit. It looked like the wildflower season was just past its peak--- the grass had started to brown and many of the flowers were fading. But there was still a beautiful spectrum of yellows, purples, reds, and blues. (And, lower down the mountain, the omnipresent orange California poppies.) I saw several butterflies as well. I haven't been able to identify one of the flowers I liked most. It was a purple spiked ball with tiny blue flowerets emerging from a few of the spikes.
I was struck once again by how alien some of the native California vegetation looks--- all spiky and strangely textured or colored. I'm just not used to living someplace where the plants are so dry-adapted.