Fodor's Expert Review Castillo de San Marcos
This castle was built in the 13th century on the site of a mosque. Created by Alfonso X, it was later home to the Duke of Medinaceli. Among the guests were Christopher Columbus, who tried unsuccessfully to persuade the duke to finance his voyage west, and Juan de la Cosa, who, within these walls, drew up the first map ever to include the Americas. The red lettering on the walls is a 19th-century addition. Visits are by tour only (in English at 11:30), which must be booked by phone or email; Tuesday, Thursday, and Saturday visits include the next-door bodega for a fee.