Short but nasty (in a good way!) hike on a VERY unimproved trail -- might be the single most butt-kickingly wildernessy mile and a half within 30 miles of SF.

You will find nothing in the way of switchbacks, bridges, or visibility beyond the next few meters here. Expect scrambling-steep slopes with no flats the entire way, extremely loose soil, rocky stream crossings (dry or wet depending on the season), path widths measured in inches, piles of brush, and logs that need to be gone over or under. It's not even that scenic, really... there are hundreds of prettier trails in the Bay Area.

There are only three nice things about Colier Spring Trail: it's quite shady, there's no poison oak, and chances are excellent you'll have the whole thing to yourself. Even on a day when the rest of the lake area is choked with families, mountain bikers, joggers, dog-walkers, and retirees you can find total solitude on this path.

Do everyone a favor and don't bring any person or animal that will not enjoy all of the above. It would be even more unpleasant to go DOWN this trail if someone in your party decides they can't make it, so don't think you can bail halfway either.

Once you get to Colier Spring crossroads, there's a bench you can sit on and have a good cry. Then the shortest way home is Lower Northside Trail to the Lagunitas-Rock Spring fire road, and thence to the Lagunitas Picnic Area off Sky Oaks where you parked. The whole ordeal is just under 5 miles but you'll get a quick taste of all the emotions you go through in a much longer wilderness trip!

Here's a map:

http://www.marinwater.org/documents/2010.10.20_VstrMap_color.pdf

PS To make things even more confusing, it's spelled "Colier" on the map but "Collier" on the signs in the woods.

GPS track captured with RunKeeper. Notice the slope of Colier Spring Trail.

http://runkeeper.com/user/niallk/activity/105311702

Four crossings of the Lagunitas Creek without bridges. Fording the creek in the rainy season will likely be pretty difficult.

Some bouldering involved. If you have a pet or small child you may need to carry with one hand while stabilizing yourself on the rocks.