The hook
A stretch of old Highway 1 so treacherous they finally drilled a tunnel around it, now a flat cliff-edge trail you get to walk or ride with no cars.
01Why it's worth it
For decades this was the white-knuckle piece of Highway 1, a two-lane road clinging to a crumbling cliff that landslides kept closing, sometimes for months. In 2013 they rerouted the highway through the Tom Lantos Tunnels and handed the old roadbed to walkers and cyclists. So you get a wide, paved, 1.3-mile balcony hung on the cliff face, with the ocean straight down on one side and benches and spotting scopes for whales and peregrine falcons. It's the rare place where the appeal is that something dangerous was made calm: you stroll a road people used to grip the wheel on. And the stretch has its icon: the Devil's Slide bunker, a WWII fire-control station perched impossibly on a rock pinnacle just south of the trail — built in 1943 to triangulate targets for the coastal batteries, abandoned since, graffiti-crowned, and unreachable (the pillar is private property and the scramble has killed people). It's the most photographed concrete on the coastside; the Highway 1 pull-out south of the tunnels frames it best.
02How to experience it
Park at either end (the north lot near Pacifica or the south near Gray Whale Cove) and go out and back; it's flat and family-easy. On a gravel bike it's a smooth, quick spin with the best cliff views on the north coast. Drop down to Gray Whale Cove beach at the south end if the tide's friendly.