Day trip to Havana from Miami. Is it practical?
 

It looks like I could do a day trip to Havana from Miami, leaving on a 6:50 a.m. flight and arriving at 8 a.m. The return to Miami is at 10:20 p.m. I'd have to be at Havana by 7:30–7:45 p.m. to play it safe, I reckon.

With no checked baggage, I reckon I could get through customs in Havana within an hour of landing. So, that's about 10 hours on the ground in Havana.

Is that practical?

I'd want to see old town Havana, get some pictures and then get a late lunch/early dinner before flying home.

Sure, and you can hire a local guide to help you make the most of your Habana Vieja time.

What is there to do practically besides see the old town, have some drinks, ride in some old cars and get some pictures? Obviously, you want to stay in or very close to Havana because of the short time.

Walk the five plazas; see the architecture; visit the printmaking studio (Taller de Grafica) at the cathedral square; have a beer or two and take in the environment at the Plaza Vieja; go to the artists' market (mercado San Jose), stroll on the seaside malecon), maybe go to Hemingway's home (9 miles away); have a daiquiri at La Floridita; definitely have drive in a 50's convertible.

While in Havana, I encountered a young American couple that had flown down to Havana for the day from Ft. Lauderdale. That couple expressed regret for not staying a bit longer. It's doable and very affordable.