Bay seniors know better than to visit Muir Woods during the summer. The crowds are monstrous. The parking is ridiculous. But for two days, after closing time, you’re invited to a much more haunting way to see this natural treasure – a guided hike of Muir Woods by night. There are only two of these spooky jaunts – so sign up fast – on July 14 from 7 to 9, and August 13 from 6:30 to 8:30. It’s a very easy trek over two miles of paved paths. Reservations are absolutely required. Call 415-388-2596.