Crissy Field Ave, Presidio

I don't say this often, and these occur even less frequently, but this is no-holds-bar one of my favorite places to be on a sunny day in the city. Crissy Field has practically every activity needed for a park - large fields, barbecue pits (free), decent parking (also free), lots of trees for slacklines or organized games of Capture the Flag, beaches, and stunning views of the bay and the Golden Gate Bridge.

Day or night, this is a fun, safe neighborhood to hang out in. For those outdoorsy indoor types, Planet Granite San Francisco, one of the best climbing gyms in the country, offers some great topropes, better bouldering, and the best views available from ANY indoor climbing gym. Just about everybody seems to be tossing around a frisbee, throwing a football, tanning on the beach (weather permitting), or sailing their boat.

More than anything, Crissy Field serves as a great reminder as to why it is such a pleasure to live in a city surrounded by water on three sides - the views are striking from almost anywhere. I can't think of any obvious or immediate down side other than the fact that it is such a great spot that everyone seems to want to go hang out there.