Throughout the long history of Naples, the fortifications were enlarged, reinforced and updated; in places, the original wall is still visible. From the time of ancient Neapolis, some of the east-west roads have survived, and today these form, with the transversal roads, a series of blocks running perpendicular to the slope. Elsewhere in the city, an irregular network and the orthogonal layout testify to the medieval and Spanish eras in its history. Other urban features of Naples, such as the Piazza del Mercato, which dates to the 19th century, reflect its more recent period.
This exceptional urban framework also includes major monuments and sites, including the Castel Nuovo and its triumphal arch near the port, the "Charteuse" of Saint Martin on the Vomero Hill and the Villa Floridiana at the edge of the city. The city's religious and secular architecture illustrates a succession of styles, including Romanesque, provincial Gothic, Catalan, Tuscan, Renaissance, Baroque, Classical and Neoclassical. Sprinkled with religious buildings adorned with rich interiors, the urban fabric is extremely dense.