Cairns, cairns, everywhere!
This is an easy trail near Lake Pleasant with some decent scenery and relative solitude. Oddly, the trail never actually reaches Spring Valley (as shown on my map), or is really even that close to it, but it still has its perks. I would recommend this trip for a family with kids or as a starting point for other trips into this wilderness. The trail ends at the bottom Garfias Wash, which travels pretty deep into the Hells Canyon Wilderness.
The hike begins about 100 feet from the parking area down Castle Hot Springs rd. Basically, as soon as the creekbed is easily accessible from the road, hop on in. Once you're down there, look around for a gigantic cairn in the middle of the wide swath. Head towards this cairn, and keep your eye out for another and a sign on the other side of the creek. This sign marks the wilderness boundary, and the trailhead and register are about 15 feet farther.
From the trailhead, the trail immediately climbs about 80 feet (at most) and then turns you sharply left. After this point, the trail becomes a cairn-fest. Earlier this year, the American Hiking Society did some serious maintenance on this trail. The maintenance is much appreciated and made my outing much more pleasant, but man, they went a little overboard with the cairns. If you happen to get lost on this trail now, you shouldn't be venturing anywhere outside of your house. This trail is CAIRNED! In addition, the American Hiking Society dug several runoff channels and built steps in the steep sections. Anyway, after about a half mile the trail meets up with power lines. Sweet! These unwanted trail companions don't veer away for about another half mile, but after that you're good for the duration of the hike. The trail continues dipping in and out of washes for the next mile or so, all the way gradually moving closer to peak 2904. Eventually you reach the base of peak 2904 and begin switchbacks to the bottom of Garfias Wash. The trail maintenance ends once the switchbacks begin, but it's still very easy to follow. At the bottom of the wash a large boulder topped with a cairn marks the end of the trail. Don't stop here though... I followed Garfias Wash upstream for about a mile before I stopped and went through my normal "time to turn around" procedure (snack, shade, read whatever novel I brought along). On the way back through Garfias Wash, make sure to keep your eye out for the cairn that marks the trail, because it's very easy to pass unnoticed. The hike out of the wash is nice, because up until this point, the trail hasn't offered much of a workout. Return the way you came.
Another option would be to turn left into Garfias Wash, hike the wash down to Castle Creek, and hike Castle Creek back up to your car. This looks feasible and would make for a pretty decent loop, although I've certainly never tried it.
I will likely return to this trail, but only to explore farther up Garfias Wash and deeper into the wilderness.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.