A church at the site of current Santa Marta was present by the 13th century, originally dedicated to St Calimero. In 1386, it housed the flagellant Confraternity of the Disciplini of St Marta, who added a hospice and rededicated the church. The church has been refurbished over the centuries. The facade dates to 1720–1730.
The interior ceiling has a late 17th-century fresco, depicting the Glory of St Martha, by Giovanni Battista and Carlo Pozzo, and the church houses a 17th-century processional statue on the main altar of the Madonna of the Rosary and Child. The altar has 16th century marble sculpture busts of the apostles; the altar was refurbished in 1816 likely by Giuseppe Bovara. The lateral altars have statues of Santa Marta and San Antonio di Padova.
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.