This hike is the shortest of the NorCal six pack, but I went with a friend, and had a wonderful three-hour trip up and down to the peak of Mount Umunhum. While the trail was pretty busy, including a few dozen cyclists, it was never crowded, and we had plenty of time to ourselves. Three charming wooden bridges, plenty of shady trees, and incredible views of the entire South Bay made for a day I won't soon forget. Once you reach the top of Mount Umunhum, you are able to visit a Native American sacred circle, although I only observed respectfully from a distance, and I learned that the mountain is named after a tribal word for hummingbird. The remains of an Air Force station are most clearly visible because of the four-to-five story RADAR tower that looks like something out of a James Bond novel. My friend and I speculated over some of the secrets it likely still holds inside its welded shut doors.