Balboa Park was mentioned in a discussion at Yahoo! Groups. On their website it says:

Balboa Park - the nation’s largest urban cultural park. Home to 15 major museums, renowned performing arts venues, beautiful gardens and the San Diego Zoo, the Park has an ever-changing calendar of museum exhibitions, plays, musicals, concerts, and classes—all in the beautiful and timeless setting of this must-see San Diego attraction.

The 15 museums alone would keep me busy for a long time, then there are the gardens and the Zoo. Balboa Park is added to my wishlist of places to go.