“ They ordered the digging of two mines beneath the walls towards the west, one hundred feet apart, that we would not have been able to stop with counter-mines. One extended beneath one of the towers: after setting fire to the heap, the tower was eradicated from its foundations and several rocks the size of oxen flew through the air”. This chronicle by an unknown author describes the siege of Mondolfo in 1517 at the hands of Lorenzino de’ Medici’s troops, when the besiegers—after digging a long minetunnel beneath the so-called ‘tower of the bakery’ (owing to the presence of a public bakery on the site)—set fire to the fuses: large quantities of gunpowder exploded and Mondolfo’s fortifications were shattered into rocks ‘large as oxen’ which were flung high up into the air. Following this event, the Bastione S. Anna bastion was erected along the town’s curtain walls, towards the southwest, probably to replace the former tower—damaged beyond repair during the siege—and to adapt the walled town to the onset of firearms in the second quarter of the 16th century, at a time when the Sangallo brothers were erecting similar fortifications along Fano’s south-eastern walls. The former tower, therefore, was replaced by a bastion erected as a reinforcement structure linking two sections of the curtain wall. The bastion had a modern design for the time and was roomier than the former towers, so that it could house a larger number of artillery pieces and relative crew. It also featured some embrasures: at least two protected ones for cannons can be seen in Mondolfo’s bastion. Though the bastion’s design cannot be attributed to the genius of Francesco di Giorgio Martini for obvious chronological reasons, the Sienese architect nonetheless played an important role in the development of the bastioned fortification, thanks to his former works and experimentation: in Mondolfo, where he designed and erected an imposing fortress, he adapted the entire defensive system of the walled town to create a formidable war machine that Lorenzino’s troops could only conquer through an act of betrayal. Once its military function ceased, the Bastione S. Anna bastion was converted into the pleasant garden of the monastery that arose near the town’s central square, namely the Monastery of St Anne (hence the bastion’s name), cloistered in 1650. Alternating work and prayer, the nuns tended to their vegetable patch and garden, which included a masonry lemon house for growing citrus trees. These were the origins of the so-called ‘Martini Garden’: after all, the most renowned architect in Mondolfo had been one of the theorists of the Italian-style garden with its carefully studied, regular geometrical patterns.