For anyone with a free day in Miami, the Frost Museum is a great place to spend the morning or afternoon. I was a bit leary that it may be more of a children's attraction, but it is definitely a great day for all ages. The Frost Museum has both indoor and outdoor exhibits with elevators that take you to 1 of 4 levels with different themes on each; my husband and I visited in the heat of Miami summer (so as you can expect, we melted).
Between the 2nd and 3rd levels is an incredible glass tank of stingrays, sharks, sea turtles, and a variety of fish in which (depending on the level) you can enjoy both from above and below. (see photos). The museum has a variety of other wildlife including birds, freshwater fish, turtles, frogs, snakes, etc. and a plethora of reading material if you come ready to learn as well. The majority of the museum is sure to keep you engaged, but the top level is a very underwhelming garden in which needed a lot of work during our visit.. if you're in a time-crunch, I'd suggest skipping this level.
Be aware -- the Frost Museum is definitely on the pricier side for standard museum prices at $30 / person on top of $15 parking. However, if you're familiar with the downtown Miami area, you may be able to locate a 'pay to park' space within walking distance that will lessen the cost of your day.
Great views of the Miami harbor & beautiful aquarium. Worth the visit! :)