We have a 4 hour layover! Anywhere to stretch our legs nearby?
4 hrs is barely enough time to get off your flight to go to the next flight, not enough time to get off the airport.
There's a medium-sized mall called the Tanforan Mall one BART stop away from the airport. You should have time to roam around in there for 90 minutes or 2 hours. There's nothing special about the mall, though. It's just your typical mall.
Or you can go to downtown Burlingame for an hour or two. You'd have to take a cab/Lyft/Uber.
Thanks for the great suggestions. We went down to the Bay Bridge and walked along the path. Also, checked out a funky art piece/ fountain and.c artists' market nearby. It was a quick out and back using the BART which is a great subway system. I definitely want to come back to SF.
Cool city with friendly people.