Via Crociferi is a tiny street parallel to Via Etnea to the west. While Piazza Duomo is the center of the city's civic power, Via Crociferi is the center of its religious power. Church is stacked upon church, all in the grand baroque style. I believe there are 9 churches within 200 yards of each other, something like that.
Although Via Crociferi is parallel, it is much higher up than Via Etnea due to the ancient lava flow it's built upon. It's accessed from the extremely steep Via San Giuliano or by stairs.
Unfortunately it is rare to find one of the churches open to the public. I don't know why.
Connecting the Via to the streets below is a wide staircase that is lined with pubs. This is "Nevsky", so-called after the pub of the same name which attracts the most socialist oriented crowd in town. This is one of THE night spots in Catania, by the way, and Via Crociferi at night, isolated above the crowd, is where most of the zone's drug deals go down.
This mixture of the sacred and the profane has always fascinated me.
The arch at the southern end of the Via was built so that the nuns living in a cloister could travel to church without having to go outside. In earthquake-prone Catania such a walkway was considered inordinately dangerous (its collapse would block the escape route of a number of streets), but it was built all the same, and the nuns still use it. In fact, they only step outside once a year, in order to offer a song to St. Agata during her festival (see my travelogue, 14th Installment, for much more detailed information).