This paper deals with the documentation and digital survey of fortifications in the historic city of Piombino. During the Renaissance the fortified perimeter of the city was considerably enlarged, both because of the will of the Lords of Piombino, the Appiani, to build a fortified citadel, deeming the previous urban palace inadequate for the ruling family, and to improve the defenses by land with the construction of a rivellino in front of the north door and of a fortress to the east. The defenses, conquered by Valentino’s troops in 1502, were redesigned by Leonardo da Vinci, as documented in the pages of Code II of Madrid, which contains drawings and calculations for the construction of the works. The present project, started in April 2018, plans to carry out an accurate digital survey of fortifications, in order to provide the basis for graphic documentation on which to base further cognitive investigations, from archaeological ones to diagnostic ones. The survey operations were carried out with today’s digital technologies, laser scanners and cameras, creating reliable point clouds and three-dimensional models mapped with texture, from which to extract 2D drawings. The study of the sources, of the texts of Leonardo’s scholars and accurate archaeological investigations will provide the opportunity to further analyze Leonardo’s intervention on the still existing structures.