The climax of the Carnival celebrations is traditionally celebrated on the last Thursday, called Zioba (Fat Thursday). Even today, in addition to the excitement of Mardi Gras, the closing day of the two-week carnival, it is on Thursdays that the biggest theatrical Venetian events and parties take place.
Zioba Grasso dates back to the victory of Doge Vitale Michieli II over Ulrico the Patriarch of Aquileia.
In 1162 the Serenissima took Ulrico prisoner together with 12 parish priests allied to the Friulian feudal lords. These were the conspirators of a rebellion for control over the Grado salt pans. The patriarch of Grado, Enrico Dandolo, had to flee to Venice. Ulrich's captivity ended when he promised to pay an annual tribute to Venice of 12 loaves of bread, 12 pigs and 1 bull.
Zioba Grasso ('the day of the hunt') became the anniversary of this victory, which was celebrated in St Mark's Square for many years. The celebrations saw a bull (symbolising Ulrich) and 12 pigs (the 12 parish priests) sacrificed for the glory of Venice.
It became customary to give a piece of meat to each Senator of the Republic and to distribute bread to prisoners. The victory over the Friulian feudal lords and Ulrico was also commemorated at Zioba Grasso in the Sala del Piovego in the Doge's Palace. There the Doge and Senators beat the wooden castles with iron bars symbolising the victory over the feudal lords.
To the delight of Venice, the feast and tribute celebrated there continued even after the decline of the Patriarchate of Aquileia. With the banning of pig and bull killing, the celebrations became less bloody.
From the 16th century until the fall of the Serenissima in 1797, Zioba Grasso took place in St Mark's Square, in the presence of the Doge and other dignitaries. There, a wooden machine in the shape of a square tower would set off fireworks. The favourite spectacle then was an acrobat walking down a rope from St Mark's Bell Tower to the Piazza. Many died trying to perform these feats.
Among the Venetians, the game 'The Power of Hercules' was very popular. In this game, the two main factions into which the Venetian people were divided, Castellani and Nicolotti, challenged each other. Each faction creates an extraordinary human pyramid, either on barges on the water or on land. The people's shouts and applause determine the winning faction. Another annual event that took place before the fireworks display was the Moresco, the military dance of the 'arsenalotti' (Arsenal workers).