Sant'Elmo is the name of both a hill and a fortress in Naples, 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. Pedro Alvarez de Toledo, the Spanish viceroy, had the fortress rebuilt between 1537 and 1546. The fortress is a star-shaped castle with six ramparts. During the revolution of 1647, so-called “Masaniello’s Revolt”, the Spanish viceroy took refuge in the fortress to escape the revolutionaries. Sant’Elmo was also the symbol of the short period of the Neapolitan Republic of 1799.The fortress has been restored to public use since 1980 and houses the "Bruno Molajoli" Art History museum. (http://en.wikipedia.org/wiki/Sant%27Elmo)