The Cathedral of St. Peter the Apostle was built at the end of the 18th century. The façade was added in the second half of the 19^th century, due to the subsides of the pope who was born in Senigallia, Pious IX.

It underwent various renovation works due to the earthquakes of this area.

Inside the plan of the cathedral is in the shape of a Latin cross, with a nave and two aisles divided by pillars and a dome- shaped vault. There are very interesting works inside the church, such as the Mannerist works by Federico Barocci ( Rest on the flight into Egypt), by Ercole Ramazzani (Madonna of Hope), Domenico Corvi ( Saint Paulino and Holy Mary Magdalene) and Alessandro Tiarini (Assumption).

Modern painting by Silvio Galimberti represent the delivery of the keys of Heaven from Jesus to Peter and the sanctification of Peter to universal shepherd of the Church. They are at the sides of the painting above the main altar, where the protectors of Senigallia and its diocese ( Saints Peter and Paolino) were painted by Tiarini from Bologna.

In the sacristy the 6^th century sarcophagus of St. Gaudentius with the symbols of the four evangelists was made by an unknown artist.

The Chapel of the Madonna della Speranza is of particular interest. It was designed by Giuseppe Ferroni, its eight Corinthian columns are made of jasper and yellow marble and inside you can admire a 16^th century painting by Ettore Ramazzani representing the Madonna of Hope.

Close to it, a new chapel is dedicated to the cult of St. Maria Goretti, who is represented in a wooden sculture in the act of forgiving her perpetrator.

Noteworthy is the richly adorned Baptistery, where Giovanni Maria Mastai Ferretti, later Pope Pius IX and sanctified by Pope John Paul II, was baptized here in 1792. The imposing bronze statue placed along the main nave is also dedicated to him.