Your visit continues with the other chapels at the back left of the Cathedral, where you can admire more 14th-century Gothic frescoes and two large canvases by Giorgio Vasari that were originally painted to decorate the Cathedral's organ. Some of the figures depicted are portraits of members of the Farnese family.
Go back towards the façade along the left nave. Almost opposite the Chapel of the Treasure of Saint Januarius you can see what remains of the ancient Basilica of Santa Restituta dating back to the fourth century. Venerated before the cult of San Gennaro had spread, Restituta was an African slave that was martyred for having converted to Christianity; she later became the patron saint of Ischia.
You should know that this 5-nave basilica was embedded in the construction of the 14th-century Gothic Cathedral. Even the small amount that remains is a rare example of paleo-Christian architecture, with its original mosaic floor and partly-ancient columns. As you can imagine, when the basilica was incorporated into the Cathedral it had to also be partially modified; for example, Gothic arches were built over the paleo-Christian columns. On the ceiling you can admire a beautiful canvas by Luca Giordano, while the 18 tondi depict Christ, the Virgin, and the Apostles. At the back of the left nave you'll find the Chapel of Santa Maria del Principio: I'd like to point out a beautiful 14th-century mosaic and two remarkable late-13th century marble bas-reliefs inside.
From the end of the nave, on the right, you can go to the Baptistery of San Giovanni in Fonte, which is considered the oldest in the Western hemisphere, even older than that of San Giovanni in Laterano in Rome. It was founded by Bishop Severus at the end of the fourth century, and its architecture has a vaguely oriental flavor with a square layout that turns into an octagon closed by a dome at the top. Make sure you don't miss the fragments of the mosaics with scenes of Jesus's life in a classical style, which reveal their Byzantine art inspiration.
FUN FACT: the Caracciolo family laid claim to all rights to the Cathedral's floor. They insisted on inserting tombstones and family coats of arms. The dispute went on for quite a while until the Cardinal resolved the matter by having the floor redone at his own expense!
