The Caltrain trip ends at Fourth and King in San Francisco. Walk along King Street a few blocks, past PacBell Park to the Embarcadero. If you haven't walked the Embarcadero for awhile, you are in for a treat. The light rail runs to the foot of Market Street, and historic streetcars serve Fisherman's Wharf. Along the way are great city and bay views, and for the history buff are high metal pylons, sidewalk plaques, and pedestal displays that recount the golden years when the waterfront ruled and shipping was king.

Continue walking past the Maritime Museum (stop awhile if you have time), over the hill to Fort Mason, and down to Marina Green. Move on to the newly restored Crissy Field Promenade and tidal marsh, where freshwater and saltwater merge for the first time in nearly a century. You will likely see windsurfers sailing into and away from the beach, for this is considered to be a world-class windsurfing area.

At the end of the Promenade, under the south anchorage of the Golden Gate Bridge, is Fort Point. You will want to spend some time here or come back later. Wide brick arches, spiral stairs, and views of the Golden Gate, plus the tools of war--mid 1800s style--make this a fascinating place for photographers and historians.

The trail to the bridge is opposite the U.S. Park Service administrative office for Fort Point. A sign points to the bridge and to Fort Point, and a stairway leads up to a series of paths and to the bridge. The uphill slope along the stairway features beautiful, wild nasturtiums in brilliant color from yellow to deep orange. Along the path to the bridge overlooking the Bay is Battery East, a three-quarter mile of earth berm with masonry enforcements built to guard the Bay in 1870.

The 1.2-mile walk on the span can be a bone-chilling experience or a warm stroll in the afternoon sun. We've had it both ways, but it's always interesting. The tourists, views, rumbling traffic, and the fog-shrouded towers produce an atmosphere like none other. We've watched hundreds of fishing boats and windsurfers near the south tower, waved goodbye to our son leaving on a Coast Guard cutter from the center span, and witnessed the grim reality of a double suicide from the north tower. Don't try to predict the bridge: it's a place to experience moment by moment.

Beyond the north tower parking lot is the Bay Trail down to East Fort Baker. We doubled under the north anchorage of the bridge, which resembles a giant erector set. The trail soon levels out at water's edge and skirts the southern edge of this old Army post. This part of the walk is filled with splendid views, but some of the best are from the water's edge in front of the Coast Guard Station Golden Gate.

Continue on the road next to the small boat dock area between two small buildings to a sign that reads "Presidio Yacht Club." Turn left and continue a short distance to the San Francisco Bay Children's Discovery Center. At the entrance, turn right up a gravel road, and follow this path up a stairway to East Road. Continue on East Road--with great views of Angel Island and Tiberon), and walk into Sausalito via Alexander Street, Second Street, and Bridgeway. Once in Sausalito, check the ferry departure times for the Red and White Ferry to Pier 43 1/2. The Golden Gate Ferry also serves Sausalito, but it docks at the Ferry Building. As time permits, enjoy the Sausalito scene of food, drink, shopping, or just people-watching.

If you drove in and parked at Crissy Field or Fisherman's Wharf, return on the Red & White Ferry to Pier 43 1/2. If you took the train, return on either ferry, but we suggest the Golden Gate Ferry, which docks at the Ferry Building. It will cut a mile or so from your walk back to the train.

And if you miss this walk on the Fourth of July, keep it on your list of things to do. It's a fun day of city walking any time of the year.