This loop through the beautiful Marin Headlands provides a great combination of beach, coastal views, and a splash of historic military sites. Not to mention, this is the only set of trails within the Marin Headlands that you can enjoy with your four-legged friends (dogs are allowed on the three trails, but they must be kept on leash).
After a nice but highly trafficked section of trail along the Rodeo Lagoon, you come upon Rodeo Beach. The beach is a great place to relax for a while before beginning the climb on the Coastal Trail, and the rocky shore just south of the beach makes for some great views. On the north side of the beach lies Fort Cronkhite, a World War II military post that has been preserved and converted to offices for the National Park Service, which oversees the Golden Gate National Recreation Area.
On the climb up Coastal View Trail, the views of the coastline only improve and glimpses of San Francisco and the Golden Gate Bridge can be seen in the distance. Along the trail there are multiple abandoned (and mostly sealed) World War II bunkers. One of these bunkers, Battery Townsley, features one of its 16-inch guns, and the park offers tours of the battery on the first Sunday of every month.
A small detour from the loop, up to Hill 88, offers another collection of great views and interesting military history. Entering the hilltop through the original barbwire-topped fence and passing the long abandoned guard booth is an interesting and unique experience. The hilltop is home to a number of empty, and now graffiti-adorned, buildings and two large upright structures that at one point held the radar systems that once lived here to support the missile installation at the Nike-88 site down the hill.
The remainder of the hike provides enjoyable views of Mount Tamalpais and the rolling hills surrounding it.