Pretty much any of the boat tours leaving from the Bayside piers offer a great hour-and-a-half spin through the Bay. The views of downtown are beautiful, even on an overcast day. And most guides know who owns all of the mansions located on Star Island, Fisher Island, and the rest of the exclusive islands around Miami. To be able to get fairly close views of the (empty) homes of the likes J.Lo, Madonna, and Enrique Iglesias felt a lot like taking a star tour in L.A., except one could actually see most of the homes with unimpeded views. The boat tour is a nice complement to the ubiquitous bus/shuttle tours operated by Miami Nice Tours, or Paradise Tour Co. Both are a great way to see much of the city to either get a lay of the land or if one is only visiting for a couple days.