Naples' cathedral dates from the fourth century, when the basilica of Santa Restituta was founded. In the late 600s the cathedral of Santa Stefania was constructed perpendicular to the original basilica, and at the end of the 13th century the current Duomo was built over Santa Stefania, incorporating Santa Restituta as a side chapel. The bland, 19th-century neo-Gothic façade is tucked away in an unprepossessing, heavily congested side street, so little prepares the visitor for the splendours within.
The gloom of the 100m (328ft) Latin-cross interior fails to obscure the fine gilt coffered ceiling (1621) and the paintings by Luca Giordano and his school. The large chapel on the right is the Cappella di San Gennaro, or Museo del Tesoro, which contains the relics of San Gennaro and a large number of bronze and silver statues of saints (many others are kept in the sacristy, and only put on public display in May and September).
The most famous remains of all are kept in a 14th-century French silver bust and two vials in a strongbox behind the altar. The bust contains Gennaro's skull; the vials his congealed blood. Three times a year the blood allegedly liquefies, most dramatically on Gennaro's feast day, 19 September. The chapel has a magnificent gilded bronze gate by Cosimo Fanzago (1668) and some fine frescoes by Domenichino (1631-43), depicting miraculous episodes from the saint's life. Above the right-hand altar, San Gennaro emerges unscathed from a fiery furnace in a painting by Giuseppe Ribera.
Back in the main church, to the right of the high altar, the chapel of Sant'Aspreno and the Minutolo family chapel have original Gothic decorations. Below the high altar, a magnificent late 16th-century succorpo or confessio (small chapel) by Tommaso Malvito houses a fine statue of a kneeling Cardinal Carafa and an urn containing more of San Gennaro's bones. The entrance to Santa Restituta is on the left side of the nave; inside, the ceiling painting is attributed to Luca Giordano. Carry on into the fourth-century baptistry - the oldest building of its kind in the West. Beneath the baptistry, the archaeological area showcases Greek and Roman walls, columns and roads, along with early Christian mosaics from the original Santa Stefania cathedral.