Part of the city walls survive of the ancient Greek nucleus of Naples and, despite the high density of settlement over more than 25 centuries, the original Ippodamic plan, built around three 'plateiai', the main axes east-west - identifiable in present day topography as the roads B. Croce-San Biagio dei Librai, Tribunali and Anticaglia-Pisanelli - that intersect other narrower north-south road axes, the 'stenopoi', forming an orthogonal network of 'insule' - blocks. A large part of the religious buildings in this ancient centre is from the Angevin period, while the greater part of the residential construction is sixteenth-century. The street axis that corresponds to the smaller 'plateia' called Spaccanapoli is so-named because it seems to split the city into two equal parts. The street delineates, on two sides, a sequence of buildings of great architectural interest, such as the church of Gesu' Nuovo, with the splendid Immacolata steeple, the churches of Santa Chiara and S. Domenico and, finally, the Sansevero chapel and the church of S. Gregorio Armeno. The middle 'plateia', that runs along present-day Via dei Tribunali, incorporated into an extremely rich and stratified urban fabric, is flanked by magnificent Gothic, Renaissance and Baroque-style churches, with an abundance of precious paintings and works of art, such as the church of S. Pietro a Maiella, the Pio Monte della Misericordia, and the Duomo itself, an admirable example of superimposition of plans and styles. The last 'plateia' corresponds to what was the highest area of the city, being transformed over the centuries from area of acropolises to that of monasteries, then hospitals and finally, of prestigious cultural institutions, adapting the ancient monasteries to new functions.