The present cathedral in Angevin Gothic style (Italian: gotico angioino) was commissioned by King Charles I of Anjou.

The cathedral gives access to the archaeological remains in the crypt of the neighbouring original palaeochristian church of Santa Restituta where there is a Greek wall belonging to the temple of Apollo, in opus reticulatum.

Another attraction of the interior is the Royal Chapel of the Treasure of San Gennaro, with frescoes by Domenichino and Giovanni Lanfranco, altarpieces by Domenichino, Massimo Stanzione and Jusepe Ribera, the rich high altar by Francesco Solimena, the bronze railing by Cosimo Fanzago and other artworks, including a reliquary by French masters of the 14th century.

A recent hypothesis by Garlaschelli, Ramaccini, and Della Sala is that the vial contains a thixotropic gel,[1][2] he also explained on the Blood Miracle of Riddles of the Dead series on National Geographic Channel.

Researchers have proposed specifically a suspension of hydrated iron oxide, FeO(OH), which reproduces the color and behavior of the 'blood' in the ampoule.