San Marcello al Corso was built before 418, when Pope Boniface I was elected there. Pope Adrian I, in the 8th century, built a church on the same place, which is currently under the modern church. On 22 May 1519, a fire destroyed the church. The money collected for its rebuilding was used to bribe the landsknechts, who were pillaging the city during the Sack of Rome (1527).
The work was continued by Antonio da Sangallo the Younger, who rebuilt the church, but a Tiber flood damaged it again in 1530. It was only in 1592–1597 that the church was completed with a facade by Carlo Fontana, commissioned by Monsignor Marcantonio Cataldi Boncompagni. The exterior travertine statues were sculpted by Francesco Cavallini, and the stucco bas-relief over the entrance, with depicts San Filippo Benizio, was created by Antonio Raggi.
Under the main altar, decorated with 12th century opus sectile, are the relics of several saints, which include those of Pope Marcellus as well as Digna and Emerita. The last chapel on the left is dedicated to St Philip Benizi. The late-Baroque decoration contains sculptures by Francesco Cavallini and reliefs by Ercole Ferrata and Antonio Raggi. The first chapel on the left has the double tomb of Cardinal Giovanni Michiel and his grandson Antonio Orso sculpted by Jacopo Sansovino.
The church is administered and owned by the Servite Order since 1369.
References:Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.