One day
Start in the Walled City at the Plaza de la Independencia and the cathedral, walk the pastel length of Calle 59 between the two gates, and climb the Puerta de Tierra wall walk. Take a taxi up to the Fuerte de San Miguel for the Maya museum and the Gulf view, eat pan de cazón at a market cocina, and end with a malecón sunset and, if it's on, the Puerta de Tierra light show.