Castel Sant'Elmo is a medieval fortress located on a hilltop near the Certosa di San Martino, overlooking Naples, Italy. The name "Sant'Elmo" derives from a former 10th-century church, Sant'Erasmo, shortened to "Ermo" and, finally altered to "Elmo". It presently serves as a museum, exhibition hall, and offices. While most visitors forgo visiting Castle Sant’Elmo, the 360° panoramic views of the city and the bay from the castle’s terrace are worth the trip. The Novecento a Napoli Museum is housed in the ex-High Prison, Carcere Alto in Piazza d’Armi and features an impressive collection of 20th Century (Neapolitan) Modern Art.