Summary 
| Difficulty | 2 Beginner-intermediate |
| Length | 3.4 miles round trip or 3.7 miles for loop |
| Starting Elevation |
7200 feet |
| Cumulative Elevation Change |
+600, -600 round trip |
| Navigation | Road, marked trail and map |
| Time | Few hours |
| Season | December through mid-April |
| Snowmobiles Use | Not permitted except between mileage points 1 and 2. [Please report illegal use of snowmobiles in this area.] |
| USGS Topo | 7.5' series, Norden |
| Start | The plowed loading zone on the north side of Interstate 80 at the Castle Peak Area and Boreal Ridge exit. Parking is at the Donner Pass Sno-Park located at the east end of the frontage road on the south side of the interstate at the same exit. |
Description
The road that runs through Castle Valley may well be the busiest backcountry ski trail in California. On a fair-weather weekend day or holiday you can expect the Donner Pass Sno-Park to fill to capacity and more than 200 skiers and snowshoers (plus a bunch of dogs) to visit the valley. The mix seems to be about 50-50 skiers and snowshoers.
As far as navigation is concerned, finding your way up Castle Valley is straight forward though you may not be able to recognize the road in places and the blue diamonds that mark it are far and few between in the sparely wooded areas.
In itself, the tour through Castle Valley is nice but popular primarily because it is easily accessible. But many of the visitors pass through the valley because it is the gateway to Round Valley and Peter Grubb Hut, Castle Peak and the ridge between Castle and Basin peaks that offer countless opportunities to crank turns.
At the head of Castle Valley a 0.1 mile, 100-foot climb leads to Castle Pass and is an excellent extension of this tour. At the pass the views open up — to the southeast are the valley you just ascended and alpine ski areas and ridges beyond, and starting from the northeast and sweeping north and west is a panorama that takes in Castle Peak, Basin Peak and countless other peaks and ridges.
The downside to visiting Castle Valley raises its ugly head when the snow conditions are poor. It is a steady climb up the valley and that makes the return a continuous downhill run. When the snow is rutted and especially when the snow is frozen the descent is more difficult than the stated beginner-intermediate.
An alternate return route, thus avoiding the heavily used path up the valley, can be found on the opposite side of the valley from which you ascend. In theory this too is marked with blue diamonds, but they are hard to follow in the moderately heavy wooded areas. But the loop is easy to make because it simply circles the valley.
Mileage Log
Numbers in parentheses
correspond to mileage points on map
Waypoint 1 to 2
Miles: 0.0 - 0.3
Elevation change: +100 feet
From the trailhead (1) ski east on the snow-covered road that parallels the interstate and then northwest for a total of 0.3 mile until you reach a road junction (2). The tour continues northwest (straight) on the road while the road to the west (left) loops around the west side of Andesite Ridge.
Waypoint 2 to 3
Miles: 0.3 - 0.5
Elevation change: Nil
Ski northwest (straight) on the road for 0.2 mile until you reach the edge of the meadow (3) in Castle Valley.
Waypoint 3 to 4
Miles: 0.5 - 1.7
Elevation change: +500 feet
Ski northwest on the road, which may be difficult to discern, for 1.2 miles until you reach the flat area (4) at the base of Castle Pass. It is a 0.1 mile and 100-foot climb from here northwest to Castle Pass (5).
Return to trailhead
Miles: 1.7 - 3.4
Elevation change: -600 feet
Retrace the route for 1.7 miles back to the trailhead (1).
To Continue on Loop Tour
Waypoint 4 to 6
Miles: 1.7 -2.9
Elevation change: -450 feet
Traverse and gradually loose elevation as you loop clockwise through the woods for 1.2 miles until you exit the woods and reach the meadow (6) in Castle Valley.
Waypoint 6 to 3
Miles: 2.9 - 3.2
Elevation change: -50 feet
Ski south along the east side of the meadow for 0.3 mile until you reach the road (3) you skied earlier.
Waypoint 3 to 1
Miles: 3.2 - 3.7
Elevation change: -100 feet
Turn southeast (left) onto the road and retrace the initial route for 0.5 mile back to the trailhead (1).
