In South Florida there are many beautiful national parks to experience:
In St. Augustine, where my heart belongs, there are a few options as well. If you have never been to St. Augustine, the oldest city in the country, I can highly recommend it. I spent many sunny days of my youth reading books on the lawn in front of Castillo de San Marcos, and this summer I brought my entire family there.
To find other national parks in Florida near you or in the rest of the country check out The National Park website