The Castello di Arechi sits on a steep rocky spur four hundred metres above the city, commanding views over the entire Gulf of Salerno and the mountains behind. Originally a Byzantine fortification, it was expanded and strengthened by the Lombard Prince Arechis II in the eighth century and later modified by the Normans, giving the structure its current layered character. The walls, towers, and cisterns that remain are some of the best-preserved early medieval military architecture in Campania.
The climb is steep — about twenty minutes on foot from the old town, or reachable by a winding road — but the panorama from the top justifies every step. On a clear day you can see south to the Cilento coast and north across the bay to the Sorrentine Peninsula. Inside the castle, a small museum displays medieval ceramics, coins, and artefacts excavated from the site. The surrounding gardens are cool and quiet even in summer, and the whole visit makes a fine half-day outing combined with the historic centre below.