It was founded by Maximian, archbishop of Ravenna, the friend of Justinian, who was born at Vistro, now Porto Vestre, a village to the south of Rovigno. He came to Pola to consecrate it in 546. He also founded a Benedictine monastery near, which soon became the richest in Istria by its connection with Ravenna, endowed the convent of S. Andrea, and built a house for the rector of the basilica.
The archbishop of Ravenna had the right of revising the decisions of the judges of Pola, a right which continued till 1331, when Pola gave herself to Venice, and probably commenced at the time of Maximian, who was appointed archbishop by Justinian in 546. He was a native of Vistro, now Porto Vestre, between Rovigno and Pola, and must have been a man of resource and great personal influence.
The wood at Vistro where the treasure was found was also given to S. Apollinare by Maximian. In 1001 Otho II. gave S. Maria and S. Andrea to the archbishop of Ravenna; afterwards they belonged to S. Mark's, Venice.