Museums for all: Familiar with a Fisherman Wharf’s museum devoted to the science of sight? Me neither. But the Truhlsen-Marmor Museum of the Eye is among 21 cultural treasures offering free admission December 3 and 4.

Announced in early November, San Francisco Free Museum Weekend attracted more than 65,000 online-only reservations in just one week (sffreemuseumweekend.com). However, day-of tickets remain.