The Basilica di San Zeno name rests partly on its architecture and partly upon the tradition that its crypt was the place of the marriage of Shakespeare's Romeo and Juliet. It stands adjacent to a Benedictine abbey, both dedicated to St Zeno of Verona.
St. Zeno died in 380. According to legend, at a site above his tomb along the Via Gallica, the first small church was erected by Theodoric the Great, king of the Ostrogoths. Erection of the present basilica and associated monastery began in the 9th century, when Bishop Ratoldus and King Pepin of Italy attended the translation of the saint's relics into the new church. This edifice was damaged or destroyed by a Magyar invasion in the early 10th-century, at which time Zeno's body was moved to the Cathedral of Santa Maria Matricolare: on May 21, 921, it was returned to its original site in the crypt of the present church. In 967, a new Romanesque edifice was built by Bishop Raterius, with the patronage of Otto I, Holy Roman Emperor.
On January 3, 1117, the church, along with most of the city, was damaged by an earthquake; the church was restored and enlarged in 1138. Work was completed in 1398 with the reconstruction of the roof and of the Gothic-style apse.
Attached to the basilica is an abbey was erected in the 9th century over a pre-existing monastery. Of the original structure, destroyed in the Napoleonic Wars, only a large brick tower and the cloisters survive. It had originally another tower and the abbot's palace. For long time the abbey was the city's official residence of the Holy Roman Emperors. In the 1980s a restoration discovered frescoes from the 12th to 15th centuries.
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.