Galleria Umberto I
Opposite the San Carlo is the grandest interior in southern Italy, the Galleria Umberto I. This great glass-roofed arcade, perhaps the largest in the world, was begun in 1887, nine years after the Galleria Vittorio Emanuele in Milan.
The arcade is cross-shaped, with a pretty mosaic of the zodiac on the floor at the centre, and its arching dome is 184ft tall. The Neapolitans do not seem to like it as much as they once did: even at high noon, you are likely to find its vast spaces deserted but for a few small clouds of forceful, grey-suited men arguing politics around the entrances.