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 beneath Castillo de San Marcos.
To find other national parks in Florida near you or in the rest of the country check out The National Park website