Duke Cosimo I de' Medici (b. 1519/r. 1537-74) ruled Florence for almost forty years.
Renaissance dukes liked to have maxims and the young Cosimo (he was only seventeen years old when he came to power) was no different. He chose festina lente (hasten slowly), which had been one of the favourite maxims of ancient Rome's first emperor, Augustus (b. 63BCE/r. 27BCE-14CE). The maxim was given visual form - a tortoise bearing on its shell a wind-filled sail.
The Palazzo Vecchio, where the duke and his family once lived (when it was known as the Palazzo Ducale), is full of images of sailing tortoises. However, there are many other examples to be seen elsewhere in the city.