Original: It is formed by two distinct building , the Fortress , built under Cosimo I de ' Medici ( 1552-53 ) , and the Cassero ( late 15th century ) , the latter used as military jail until 1959 .
Simplified: The Cassero Pisano a castel , built under Cosimo I de ' Medici the castel was used as military jail until 1959 .