Las Trampas is a big preserve west of the San Ramon Valley: quiet and isolated, 5 miles up Bollinger Canyon Road from the nearest signs of civilisation. I'm not sure that quite justifies the title "wilderness": it's no wilder than most of Mount Diablo, and feels less remote than most of Donner Canyon. And today was a popular day to hike it: New Years Eve, and the first dry day for a week.
The main attraction is Rocky Ridge, which runs from north-west to south-east with panoramic views north and south along the San Ramon Valley and west into the Bay: you can just about see San Francisco.
For once, we decided to ignore bahiker.com, whose route seems to shy away from the ridge, taking the lower Cuesta Trail rather than the Upper Trail running along the ridge. Their route also runs clockwise, ending by coming down the steep Ridge Road: this seems the wrong way around to me. Instead, we took the route suggested by California Hiking: up the Rocky Ridge Trail, along the ridge on the Upper Trail, and return descending the Elderberry Trail.
Tip: don't even bother looking for the Rocky Ridge Trail. It exists, but it's muddy and it runs parallel to the Rocky Ridge Road, which is a wide, paved fire road: much more comfortable to simply walk the road up to Upper Trail. It's a steep climb: 800 feet in 1.5 miles. At the top, the Ridge Road disappears through a locked gate into EBMUD watershed land. The Ridge Trail continues through a gate into the watershed, but you need a hiking permit to follow it: $10/year from EBMUD.
Upper Trail runs out along the ridge and to the views, which are spectacular. The clouds today are heavy, always threatening rain, but high enough that the peak of Mt. Diablo is visible. But it's cold and windy up here today: we stop for a sandwich and cool down so fast that we decide to defer the rest of lunch to the trailhead.
The book suggests am out-and-back detour on the Sycamore Trail to the Wind Caves ("hollowed openings in the sandstone outcrops") but that's a drop of 200 feet to regain so we leave it for another day. In any case, once you've started out down that trail it'd be hard to resist making it a round trip by dropping further to Devil's Hole — for the name alone — and returning to the ridge on the Devil's Hole Trail.
Return on the Elderberry Trail, which is where the mud starts; the route up to the ridge is paved, the ridge itself is stony and dry, but the descent drops through mixed grass and woodlands and rapidly gets muddy: it's a long 2 miles back to the trailhead. It's not sucking clay mud, like the Essex mud of childhood walks that'd pull the wellies right off your feet; but it's heavy and sticky enough that your boots get progressively heavier as you plough through it.
Very little wildlife out today; a couple of red-tailed hawks soaring over the ridge, but that was it. Las Trampas is mountain lion territory, although the chances of actually encountering one are pretty low; trailheads have posted instructions on what to do if you do. Be noisy; be big; don't rush it or run; and the one that gets me: "if attacked, fight back". Well, like: duh.