After rome and florence, the third great artistic center of renaissance italy was where giorgione and titian became the greatest painters of the high renaissance.

Venice, Venetian

Explanation:

After Rome and Florence, the third greatest artistic centre of Renaissance Italy was Venice. During the Venetian High Renaissance, artists such as Giorgione, Titian and Veronese developed new artistic techniques that helped them become some of the most renowed Italian artists of all time. Giorgione was the first painter to paint with oil on canvas, while Titian was one of the most versatile artists of the Venetian school.