On what day he quitted that city, and whither he went immediately after his departure, is uncertain.

The Ten wrote to Giugni on the 8th of August, saying that his presence was urgently required at Florence, since the work of fortification was going on apace, "a multitude of men being employed, and no respect being paid to feast-days and holidays." It would also seem that, toward the close of the month, he was expected at Arezzo, in order to survey and make suggestions on the defences of the city.
These points are not insignificant, since we possess a _Ricordo_ by Michelangelo, written upon an unfinished letter bearing the date "Venice, September 10," which has been taken to imply that he had been resident in Venice fourteen days--that is, from the 28th of August.
None of his contemporaries or biographers mention a visit to Venice at the end of August 1529.

It has, therefore, been conjectured that he went there after leaving Ferrara, but that his mission was one of a very secret nature.

This seems inconsistent with the impatient desire expressed by the War Office for his return to Florence after the 8th of August.

Allowing for exchange of letters and rate of travelling, Michelangelo could not have reached home much before the 15th.