The Santa Maria Maggiore Church in the Piazzetta Pietrasanta in Naples was originally constructed in the 6th century. its present architecture, however, is the result of a 17th century reconstruction. Remains of the early Christian basilica can still be seen in the present crypt.
Santa Maria Maggiore Church Naples
Useful information

Address: Piazzetta Pietrasanta, 17-18 – 80138 Napoli. Phone: 081 19230565. Opening times: From 10:00 till 20:00. Ticket price: Free.
(Note that opening times and admission may be subject to change.)
History and description
The Chiesa di Santa Maria Maggiore alla Pietrasanta was the first church in Naples to be dedicated to the Madonna. It had been constructed on top of the ruins of a Greek temple dedicated to Diana. The man responsible for its construction was a bishop called Pomponius, who had been told in a dream to construct the church precisely in that spot. There might also have been some strategy involved. In those days, the population believed that the devil, dressed as as a pig, used to roam the area around the temple. The new church was meant to scare the devil away.
The 6th century church was completely reconstructed in the middle of the 17th century. The architect responsible for this Baroque reconstruction was Cosimo Fanzago. Fanzago was a local sculptor and architect from an aristocratic family.
The Romanesque-style campanile had already been added in the 11th century. It is the oldest bell tower of the city.
Legend of the Sacred Stone
There is supposed to be an ancient sacred stone with an incision of a cross, hidden somewhere inside (probably) the crypt. Whoever kisses the cross, will have all their sins forgiven. It is this “holy stone” (pietra santa, in Italian) which has given the square its name.
What to see
The terracotta and majolica floor decorations are an 18th century addition.
The facade is flanked by the Chapel of the Savior, with a polychrome marble altar. The chapel was renovated in the late 18th century.