San Nicolò l'Arena, Baroque church in Catania, Italy.

San Nicolò l'Arena is a Baroque church on Piazza Dante in Catania, begun in 1687 to Giovanni Battista Contini's design. Its unfinished facade shows half-complete columns and rows of holes for marble facing. Inside, massive pilasters divide three naves; the dome, raised in 1780 by Stefano Ittar, reaches about 66 m, and the church covers over 1,500 m².

Construction began in 1687 but the 1693 earthquake caused severe damage to the building. Reconstruction efforts continued through the 18th century, shaping the current Baroque design.

The name San Nicolò l'Arena comes from the monks' devotion to Saint Nicholas of Bari and from the red sand, called rena rossa, of the first monastery at Nicolosi, founded on 28 November 1558. The vast interior was built to hold crowds during the September procession of the Santo Chiodo. The wooden choir stalls around the main altar were carved by Nicolò Bagnasco.

The unfinished facade faces Piazza Dante, where the half-built columns and rows of holes for marble facing are visible from the square. The interior is entered from this side; the transept floor holds the 1841 sundial, and the dome, raised in 1780 and restored between 1999 and 2012, stands at the crossing of nave and transept.

The floor contains a working sundial from 1841 designed by astronomers Wolfrang Sartorius and Christian Peters. This astronomical marking shows how science was woven into the church and still functions on sunny days.