Sant'Elmo is the name of both a hill and a fortress located near the Certosa di San Martino. Together, the structures overlook Naples and are the most visible landmarks in the city. The name "Sant'Elmo" is from an old 10th-century church, Sant'Erasmo, that name being shortened to "Ermo" and, finally, "Elmo".
The fortress was started in 1329 under Robert of Anjou and completed in 1343, the year of his death. The fortress is a star-shaped castle with six ramparts. The fortress has been restored to public use since 1980 and houses the "Bruno Molajoli" Art History museum.