Alternate route to
Directions: From the parking lot for MT. Sanitas described above, go west on Mapleton/Sunshine canyon for about 2 miles. You'll come to a hairpin turn to the left where the road goes uphill sharply. Park on the right. There are no "spaces," but there is room for a small handful of cars. I've never seen more than one other car parked here. I haven't calculated mileage, but you should be able to get to the top of Sanitas in an hour or so. It's likely between 1 and 2 miles.
The trail is rougher but shorter than the main Sanitas trail. Also much emptier. There are numerous other trails in this vicinity. The one I describe here seems to get the most use. I believe there is a Boulder Open Space boundary sign. I also believe all of this is on Open Space. The trail goes up sharply from the car park at first, bears right and splits a short way after it bears right (south). Either fork gets to the same place; the left fork is more direct, and steeper. If you take the right fork, probably the main trail, you'll wind south, then up, then north. If you take the left fork it's mostly up, until the trail fades in a meadow. At that point if you just continue straight for a few minutes you'll cross the main trail. Go left, uphill. There are side trails you can explore, but Sanitas is directly east. To get there, this trail goes downhill to a valley. Geologically, the bottom of this valley marks the boundary between the red sedimentary rocks that you see up and the boundary between the plains and the mountains, and the much older rock that lies west of that. Note the color change from reddish to more of a mix. At the "unconformity" (bottom of the hill) follow the trail straight up a rocky section until you get to the ridge of which Sanitas is the high point. At that point you've reached a T. North leads to barbed wire/private property. East takes you over the edge too fast, and south gets you, in a quarter mile or so of easy walking, to the top of Sanitas. The top of Sanitas is well marked, and you probably won't be alone. From there, retrace your steps back to your car. Round trip, maybe a couple of hours. Most of this hike is a moderate walk through the woods, but there are some steep sections and some loose rocks here and there.