The interior of the St. Vincent’s church is decorated with Biblical imagery, namely tableaus about this and other saints’ lives, as well as calendar tableaus arranged according to the months of the year. Frescoes painted by Master Ognobenus of Treviso show the most extensive Istrian Romanesque cycle, painted in the Byzantium in mid-13th century. There are remains of frescoes that predate as well as that follow Ognobenus’s cycle.
The frescoes of the St. Catherine are spread over the north, south and west-facing chapel walls and represent the cycle dedicated to the legend of this saint. The central point depicts the Virgo with the Child, next to which St. Catherine extends her hand to Christ’s, whose touching fingers symbolize mystic engagement. The frescoes were painted under the influence of Italian, namely Venetian 15th century painting.