Back in the days when Northern California had wet and wild winters, there was one constant. During some storm, part of Montara Mountain would come sliding down on to Route 1, the Coast Highway, cutting off the main way between Pacifica and the beach towns -- Montara, Moss Beach and Half Moon Bay. Caltrans, the agency in charge of such things for the state, had a solution: they would build a four lane road through the ranch lands behind the coast and escape the annual earth moving project. Coastal residents had a better idea: they said "Think Tunnel." And so began a prolonged tussle over planning of the sort the Bay Area is famous for.
It's just as lovely as you might expect and fully accessible to walkers and bicycles.
We do live in one of the most beautiful places in the world.