Engineer and Artist in Milan
It's not until 1482/83, when he's around 30 years old, that Leonardo moves from Florence to Milan. In the service of Duke Ludovico Sforza (1452–1508), Leonardo is not only employed as an artist but particularly as an engineer. During this time, one of Leonardo's most famous works is created: the Last Supper in the Dominican convent of Santa Maria delle Grazie. In 1499, Ludovico is driven out by the invading French, and Leonardo also leaves Milan. This marks the beginning of a period often referred to as the "Wandering Years" (1499–1512) for him. His destinations include Venice, Florence, and Milan, likely also Rome and Naples.
Return to Florence
In Florence, Leonardo works for various clients such as the Medici family and Cesare Borgia, the commander of the papal army and, ironically, the illegitimate son of Pope Alexander VI. For him, Leonardo designs war machines as well as infrastructure projects in Tuscany. During this time, he also meets the famous Renaissance thinker Niccolò Machiavelli (1469–1527). Important artworks are created during this period as well. Concurrently with Michelangelo, Leonardo is involved in the decoration of the new city council hall, where his famous Battle of Anghiari, a monumental fresco for which he made numerous preliminary sketches, is created. It remained unfinished due to many technical problems. Also during his time in Florence, Leonardo begins his most famous work: the Mona Lisa.
In the summer of 1506, Leonardo returns to Milan at the explicit request of the French occupiers. During this time, he primarily works as an artist but also makes architectural designs for the Governor's Palace. His particular interest during this time is anatomy. He participates in several autopsies and is said to have even conducted some himself at the nearby University of Pavia.
The Call to Rome
In 1512, Giuliano de' Medici, the brother of the new Pope Leo X, summons Leonardo to Rome. Some researchers believe he was the actual commissioner of the Mona Lisa. However, Pope Leo has little regard for the aging Leonardo. He is mainly employed as an engineer, working on harbor and defense structures.
The last year and a half of his life, Leonardo spends at the invitation of Francis I (1494–1547) at the royal residence of Clos Lucé in Amboise, France, supported by a royal pension—the first stable income of his life. He works very little, but it's said that the Mona Lisa remained on his easel. On May 2, 1519, Leonardo dies at the age of 67 and is buried at Château d'Amboise.