This is another great hike in the Marin Headlands just north of the Golden Gate. History buffs may find World War 2-era Fort Cronkhite of interest. Cronkite was constructed in 1941 to defend the coast north of the Golden Gate from an enemy invasion that thankfully never came. The Marin Headlands are dotted with old bunkers and artillery emplacements that were supported by Fort Cronkhite. This is one of the few remaining military facilities from the World War 2 era left largely intact. It is now one of the many attractions in the Golden Gate National Recreation Area.
This hike starts at the Tennessee Valley Trailhead. 90% of visitors head straight down the gentle Tennessee Valley Trail to Tennessee Cove, but this route is a lot tougher. Head due west from the picnic area by the parking lot, and follow the signs directing you to the Marincello Trail. Marincello gains about 600 feet as it gently ascends a ridge high above Oakwood Valley to the north before ending at the Miwok Trail. This is a fire road that is so well-maintained that a passenger sedan could easily handle it. The grade unrelentingly gains elevation, but it is pretty easy. Go straight to join the Bobcat Trail and hike 0.7 mile to its junction with the Alta Trail.
You are on top of a high ridge here with Oakwood Valley to the north, Gerbode Valley to the south, and Tennessee Valley to the west. There's no shade even though the coastal scrub grows about 6-feet-high. The views are spectacular in all directions, but fog is a frequent occurrence in late summer. Your visibility may be 100 miles or it may be 100 feet. My initial trip unfortunately was the latter, but it kept the temperature nice and cool albeit fairly humid. Long sleeves are a must if the fog is blowing in on the 20 MPH winds commonly experienced up top.
Turn right to remain on the Bobcat Trail as it gently meanders down the east side of Gerbode Valley. Gerbode Valley has a wide riparian area running beneath high ridges on 3 sides before passing through the valley's narrow mouth to join the Rodeo Valley drainage that leads to Rodeo Lagoon. The vegetation is again primarily coastal scrub, but a few large eucalyptus, Monterey pine and Monterey cypress trees provide intermittent shade. Gerbode Valley is wide, flat, well-watered and frequently encased in fog so it is a mystery to me why redwoods are absent. Perhaps there once was a redwood grove that was logged before the area was converted to pastureland in the 19th Century.
Bobcat Trail heads down 1.9 miles from the Alta-Bobcat junction to the valley floor where you want to go right across a bridge spanning the now sizable creek heading into Rodeo Lagoon. Go left at the Miwok Trail just over the bridge for 0.5 mile, then cross a bridge to the south to reach the Marin Headlands Visitor Center. Take the Coastal Trail from the visitor center 0.7 mile to Rodeo Beach. The trail reaches the south end of the beach and great views to the south of guano-encrusted Bird Island. The trail technically runs north but you'll be walking through beach sand rather than a nice trail. The north end of the beach has a nice break and is popular amongst local surfers. Head east on the small Miwok Trail that runs between Rodeo Lagoon and Mitchell Road which is right in front of the well-preserved buildings of Fort Cronkhite.
You are now on the Miwok Trail and you reach the bridge you crossed over from the Bobcat Trail approximately 1.1 mile east of Rodeo Beach. Continue up the Miwok Trail to the north as it climbs to the top of Wolf Ridge. This stretch of the Miwok Trail is steeper than the Marincello Trail, but it's not terribly difficult. You trade the expansive views of Gerbode Valley for a ridgetop stroll before descending back to the trailhead on the Old Springs Trail. Old Springs is 1.4 miles from the Bobcat-Miwok junction. There are great views of Tennessee Valley to the west as you descend, quite steeply in certain spots, through dense coastal scrub.