The Festa della Sensa ( Ascension ) was a public holiday in the Republic of Venice on the occasion of the feast of the Ascension of Christ ( in Venetian dialect Sensa ) . It commemorates two important events for the Republic : on May 9, 1000, when Doge Pietro II Orseolo rescued Dalmatian populations threatened by the Slavs . The second event took place in 1177 , when, under the Doge Sebastiano Ziani , Pope Alexander III and the Emperor Frederick Barbarossa signed in Venice Peace Treaty that ended the age-old dispute between the Papacy and the Empire. On the occasion of this festival was held the ceremony of the marriage of the sea .
On that day , every year , the Doge , on the Bucentaur , reached St. Helena at San Pietro di Castello . Waiting for the Bishop , on board a boat with gilt sides , ready to bless . To emphasize the domain of Serenissima with the sea, the Festival culminated with a sort of rite : the Doge, once it reaches the mouth of the sea and threw a gold ring into the waters .