Giustiniano had recalled his brother Giovanni from Constantinople, because he has no sons by his wife, and has appointed him to continue the construction of the new church for Venice's new patron saint.

Giovanni succeeds the aged Giustiniano, by election of the assembly, on the latter's death in 829.

The rest of his reign will be occupied by quarrels and problems, internal and external.

The first problem is the return of Obelerio degli Antenori, Doge of Venice from 804 to 811, from Constantinople after twenty years of exile.

He disembarks at Vigilia, near Malamocco, with a band of followers and lays claim to the dogeship.

Malamocco and Vigilia declare for him and both are burned by Giovanni.

Obelerio is killed and his head displayed to the people.

As the community continues to develop and as imperial power wanes, an increasingly anti-Eastern character will emerge, leading to the growth of autonomy and eventual independence.