They are sister parks. The San Diego Zoo is in San Diego (Balboa Park) and is a more traditional zoo setting. The Safari Park is out in the middle of nowhere (so to speak), is many, many times larger than the Zoo, and is dedicated to allowing animals to live and breed in a more natural setting. There are savannas hundreds of acres big with hundreds of animals. You can walk to many areas of the park (it can be A LOT of walking). You can also take a beautiful tram ride around the main savannas, and learn all about the animals from a guide. You can pay extra for some very cool tours, where you can go out into the savanna to get closer to the animals - even feed giraffe. They are also known for their rhino expertise - we did the rhino tour, and it's amazing. They are at the forefront of work to bring back an extinct breed of rhino - it's amazing and very educational. I'd recommend you check out the Safari Park web site to see more. We would highly recommend the trip.