The Castle of Mercato San Severino is the second-largest castle in Italy and was founded after 1067 by a Norman knight named Turgisio Sanseverino. The appearance of the castle today has been particularly influenced by the Angevin period. The settlement is marked by three walls: a first nucleus that includes the palatium and the so-called piazza d'armi (army square), and other rooms. The walls of the first enclosure continue south, surrounding a Franciscan convent, the village, and the corresponding church.
The second enclosure with its semicircular towers extends eastward, and it is connected to the last enclosure from the Angevin-Aragonese era, with a triangular perimeter that has a round tower at its vertex. The original size of the site was approximately 350 by 450 meters, with a total area of 157,500 square meters, equivalent to three football fields.
The third enclosure, at a lower elevation, extends eastward with a layout called 'a sperone,' and at its highest point, there is a round tower with three typical Angevin-era gun ports.
The castle was initially owned by the Sanseverino family but was eventually abandoned due to the involvement of one of its members in the Barons' Conspiracy against Ferrante. As a result, Ferrante confiscated the castle from its owners and only returned it after several years, by which time it had lost most of its military characteristics. The castle still partially preserves the chapel and the church. Saint Thomas himself visited this castle to visit his sister, Teodora, who was married to a Sanseverino. The future saint stayed at the Dominican convent. Coins, ceramics, arrowheads, and many other artifacts have been found inside the castle.
The church of the former Franciscan monastery was built probably between 1515 and 1520. It is located in the UNESCO World Heritage Site of Old Rauma. The church stands by the small stream of Raumanjoki (Rauma river).
The exact age of the Church of the Holy Cross is unknown, but it was built to serve as the monastery church of the Rauma Franciscan Friary. The monastery had been established in the early 15th century and a wooden church was built on this location around the year 1420.
The Church of the Holy Cross served the monastery until 1538, when it was abandoned for a hundred years as the Franciscan friary was disbanded in the Swedish Reformation. The church was re-established as a Lutheran church in 1640, when the nearby Church of the Holy Trinity was destroyed by fire.
The choir of the two-aisle grey granite church features medieval murals and frescoes. The white steeple of the church was built in 1816 and has served as a landmark for seafarers.