Peace and love weren't always the watchwords in San Francisco; before the Summer of Love came the specter of nuclear holocaust. Before that it was invasion by ship, and through it all, folks on the western side of town got front-row seats. Where once were coastal batteries — huge cannons meant to ward off ships from attacking the city — the military placed missiles meant to shoot down Soviet bombers. The missiles are gone now, but what's left is the poured-concrete infrastructure. The silos are in the Presidio and on Mount Sutro, but the concrete harbor defenses that protected the Golden Gate from enemy ships can be seen from Land's End to the Golden Gate Bridge and beyond, giving the tourists of today a taste of a century of advancing military intelligence.