One day is the most common Miami trip anyone takes, and the most commonly wrecked. It gets wrecked in a specific, predictable way: somebody puts Wynwood at eleven, South Beach at two and a dinner reservation in Coral Gables at eight, and spends about two hours of a nine-hour day sitting on a causeway with the meter running.
So the first thing this page does is take that decision away from you. There are two cities here, not one, and Biscayne Bay sits between them: the mainland city of Miami on the west side, the barrier-island city of Miami Beach on the east. Four causeways do all of the joining — MacArthur out of downtown, Julia Tuttle off the Wynwood and Design District side, Venetian hopping a chain of small residential islands, and the 79th Street crossing further north. No train goes over. The six miles from Wynwood to Ocean Drive take about fifteen minutes at ten on a Tuesday morning and forty to fifty at six on a Friday, with rideshare surge stacked on top of that. One crossing is a plan. Two is an afternoon you will not get back.
Which means a single Miami day is really two different days, and the one you get is decided by where you woke up. Below are both, written to the clock. Plan A is the mainland day: Wynwood, the Design District, Calle Ocho, the museum park on the downtown bayfront and a free Metromover loop through Brickell at the end of it. Plan B is the island day: sunrise on the Atlantic, the Art Deco blocks on foot, the free trolley up the island and a sunset on the bay side, which is the side of Miami Beach nobody books a hotel room on and the only side the sun actually sets over.
The second thing to understand is that a Miami day has a shape imposed on it from roughly June to October, and it is not the shape northern visitors expect. The sky builds through the morning, opens for thirty or forty minutes in the mid-afternoon, then clears into a long gold evening. That is a timetable, not a washout. Anything on water goes before noon. The storm hour goes indoors — a gallery, a long lunch, the covered blocks of a shopping street. From five o'clock you are outside again and the light is the best it will be all day. Winter takes the rain away and changes nothing else about the ordering except the price and the queue.
Third: the clock on this page is a real one. Every block below carries the travel leg that gets you to it, in minutes, at the hour you would actually be travelling. Where a stop needs a timed ticket or a reservation, it says so. Where the honest answer is that a thing does not fit in a day, it says that too, and the list of what does not fit is longer than most one-day articles admit. A half-day Everglades trip is four to five hours door to door. Key West is about three and a half hours each way. Biscayne National Park is a boat trip out of Homestead, an hour south before you board anything.
Pick your plan by your bed, not by your mood. Then cross once, late, and in the direction of your dinner.