Here’s a secret few people know about: the observation deck in tower of the De Young museum (in Golden Gate Park) is free, and open to the public during museum hours. Just tell museum staff you want to go into the tower, and they will direct you to the elevators, which take you up nine stories to the 360 degree glass enclosed observation deck. There are amazing views of the park, the Golden Gate Bridge, and western side of San Francisco—all without an admission fee.