Girolamo Bellarmato (also called Bell'Armato or Bellarmati) was born in Siena and likely spent his youth in Urbino, where he studied of mathematics, cosmography and architecture
Part of an old politically influential family, in 1525, Bellarmato's family was forced to leave Siena and were sent into exile in Ancona. The family attempteed to return to Siena, with the support of the Pope and the Florentines, but the attempts failed, and Girolamo's father and brothers Giulio and Scipione were imprisoned and executed in Siena.
Girolamo traveled extensively around Italy, teaching the mathematical sciences and perfecting his mapmaking and architecture studies. As a mapmaker, his best known work was his Choroaphia Tusciae, a woodcut map in 4 sheets published in Rome in 1 536.
In about 1538, Bellarmati moved to France as an engineer, where he oversaw the fortifications of a number of cities, including Le Havre, Dieppe and Paris.
Girolamo returned to Italy in 1546, first in Piedmont then in Modena, called by Ercole II to direct the restoration of the city walls. The Sienese invited him to return home but Bellarmato refused returning to France, where he died in the spring of 1555.