Santa Maria del Regno church, together with the annexed castle of which ruins remain today, was built in the 11th century by Giorgia, daughter of the Giudice of Torres, as a Palace Chapel. The church is mentioned in the Libellus Judicum Turritanorum of the 13th century.
The church was built in dark basalt stone by Pisan workers (the island in the Middle Ages was under strong influence from the maritime Republic of Pisa). The façade is divided into five sectors and has a salient-shaped façade. In the middle is the portal, surmounted by a double mullioned window. The whole exterior of the edifice is characterized by false columns (lesenes) and Lombard bands; on the right are the remains of the square bell tower, which is missing the upper part.
The interior, on a rectangular plan, has a nave and two aisles divided by columns whose capitals have flower motifs. The nave has a wooden trusses ceiling, while the aisles are groin vaulted. In the semi-circular apse is the large retablo, the largest 16th-century polyptych in Sardinia, located behind the high altar. The table portrays several prophets and saints, as well as episodes in the life of the Virgin Mary. In the middle, within a niche, is the wooden statue of Nostra Signora del Regno, a 'Madonna with Child' wearing royal symbols. The polyptych is dated 1515.
The church's columns have 17th-century paintings with Apostles and other Saints, while also present is a lesser retablo from the same school, a carved wooden pulpit and an epigraph celebrating the consecration of the church on May 7, 1107.
Roman Walls of Lugo are an exceptional architectural, archaeological and constructive legacy of Roman engineering, dating from the 3rd and 4th centuries AD. The Walls are built of internal and external stone facings of slate with some granite, with a core filling of a conglomerate of slate slabs and worked stone pieces from Roman buildings, interlocked with lime mortar.
Their total length of 2117 m in the shape of an oblong rectangle occupies an area of 1.68 ha. Their height varies between 8 and 10 m, with a width of 4.2 m, reaching 7 m in some specific points. The walls still contain 85 external towers, 10 gates (five of which are original and five that were opened in modern times), four staircases and two ramps providing access to the walkway along the top of the walls, one of which is internal and the other external. Each tower contained access stairs leading from the intervallum to the wall walk of town wall, of which a total of 21 have been discovered to date.
The defences of Lugo are the most complete and best preserved example of Roman military architecture in the Western Roman Empire.
Despite the renovation work carried out, the walls conserve their original layout and the construction features associated with their defensive purpose, with walls, battlements, towers, fortifications, both modern and original gates and stairways, and a moat.
Since they were built, the walls have defined the layout and growth of the city, which was declared a Historical-Artistic Ensemble in 1973, forming a part of it and becoming an emblematic structure that can be freely accessed to walk along. The local inhabitants and visitors alike have used them as an area for enjoyment and as a part of urban life for centuries.
The fortifications were added to UNESCO"s World Heritage List in late 2000 and are a popular tourist attraction.