Near the top of a newly constructed switchback trail in Muir Woods is an enormous log bench carved from a salvaged ancient redwood trunk. It’s there so hikers in the primeval Marin County forest can take a break from the hilly trek amid trees as old as 1,500 years.
It’s also there for contemplation as to how a bench weighing nearly a ton found its way onto a steep, slippery mountainside.
The answer: It came down a 700-foot long zip line from a staging area — one of the many low-tech engineering miracles performed by a National Park Service crew on the 1.5-mile Ben Johnson Trail in Muir Woods National Monument …