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The fortress of San Leo is in the Marche region and located a few miles
west of the Republic of San Marino. It dates to Roman times. First extended and
retructured in the Middle Ages, is was redesigned during the Renaissance. It is
an oustandind example of military architecture of that time. Its current appearence
reflects the strong imprint desired by Federico da Montefeltro who had the fortress
changed substantially around the second half of the 1470s. The two vast circular
keeps which frame its westward flanks were designed and realized by Francesco
di Giorgio Martini, one of Italy's greatest military architects, who was much
used by Duke Federico da Montefeltro. During the war with Cesare Borgia (1502),
Guidobaldo da Montefeltro had ordered the demolitions of his fortresses so that
they could not be usead by the enemy. Fortunately, San Leo was one of the fortresses
that escaped the order of demolition.