The San Diego Zoo is one of the biggest zoo's in the US. It will take you a whole day or more to see every species of animals there but it's a beautiful park and there are many out coves that you can rest and sit and enjoy the shade from the exotic plant life and trees. It's also located in Balboa Park which is home to several museums like the Aerospace museum and the Natural History Museum. I live 15 minutes away at the most.