I love city parks, but three U.S. parks that stand head and shoulders above all the rest and should not be missed are Central Park in New York, Golden Gate Park in San Francisco, and Balboa Park in San Diego.
Balboa Park is a city onto itself. You can explore here for a week and still not feel like you have scratched the surface. The park is a massive 1,200 acres and has 15 museums!
The park was the sight of the 1915 Panama-California Exposition, a sort of World's Fair to celebrate the completion of The Panama Canal. The fair was build around a number of Spanish Colonial Revival Buildings. The interesting fact is none of these buildings were ever meant to be permanent. They were built out of a sort of hybrid papier-mâché and plaster. They need constant attention, but almost 100 years later, they are still standing! You will often notice scaffolding in front of many of the buildings here to mend and repair them.
Exploring the park is an adventure and takes a little planning, especially if you are on a time frame. My suggestion is to start in the Park's Information Office on the Prado. You can talk to informed hosts and pick up a multitude of brochures. They will also inform you of any special events happening in the park that day.
Of course, you can't miss the zoo. I have written about it in a separate review, but many will agree that this is the best zoo in the world. But my favorite corner NOT to miss is the House of Pacific Relations and the International Cottages. This is a UN project to promote world cultures and understanding. Each country has a small cottage where volunteers and natives give an overview of their unique culture and heritage. Because it's all volunteers, some of the cottages are not open during the week. But on Sundays the village rocks! You can often catch costumed performers in the courtyard or try unique and tasty food from that country. I never miss stopping by the Denmark cottage for their tasty danish! Also try to make it on a feast or celebration day. An example is St Patrick's Day, when you can't miss The Irish Cottage, where dancers are doing jigs and you are offered a taste of corned beef and cabbage!
These suggestions just scratch the surface. Each time I visit the park I see something new and have a new adventure. Of course, the park is free (the zoo has an admission fee) and is one of the best free things to do in Southern California. The park changes all the time, but no visitor to San Diego should miss a few minutes here!