Bayfront Park is downtown Miami's front lawn on Biscayne Bay, a palm-lined open space between the towers and the water. It has lawns, walking paths, fountains, memorials and amphitheatres that bring concerts and public events into the middle of the city.
The park is most useful as a pause while exploring downtown, especially around Bayside Marketplace, the Metromover and the waterfront. Come in the late afternoon if you want the skyline and bay to do most of the work.