A small church of St. George used to be situated where the Church of St. Euphemia is located today. When St. Euphemia's sarcophagus was brought to Rovinj, the Church of St. George became too small for all the pilgrims. In the 10th century, the people of Rovinj started building a new, bigger church.
It was a three-nave church with three projected apses and wooden statues of St. George and St. Euphemia. At the beginning of the 17th century, a new gold-plated stone statue was erected which until this day remains on the altar of the Saint.
The church itself required with time more and more reparations, and the town population grew so that the people of Rovinj decided to build an even bigger church. The building process started in 1725 and lasted until 1736. Three main altars were built in 1741, and the organ was installed in 1754. The façade was designed and built in the second half of the 19th century. Many altars and paintings enrich and embellish the church from within.
https://www.inforovinj.com/eng/rovinj/znamenje/crkva-sv-eufemija.asp