The Castle of St. George (Castello di San Giorgio) was built from 1395 and finished in 1406 under commission by Francesco I Gonzaga, designed by Bartolino da Novara, one of the most renowned military architects of the time. It has as square plan with four corner towers, surrounded by a ditch with three entrances, each one with a drawbridge. In 1459 architect Luca Fancelli, commissioned by marquis Ludovico III Gonzaga, who assigned several rooms of the Corte Vecchia for the Council of Mantua called by Pope Pius II, restored the castle, which lost definitely lost its military and defensive function.References:
The Basilica of Santa Maria in Trastevere is one of the oldest churches of Rome. The basic floor plan and wall structure of the church date back to the 340s, and much of the structure to 1140-43. The first sanctuary was built in 221 and 227 by Pope Callixtus I and later completed by Pope Julius I.
The inscription on the episcopal throne states that this is the first church in Rome dedicated to Mary, mother of Jesus, although some claim that privilege belongs to the Basilica di Santa Maria Maggiore. A Christian house-church was founded here about 220 by Pope Saint Callixtus I (217-222) on the site of the Taberna meritoria, a refuge for retired soldiers. The area was made available for Christian use by Emperor Alexander Severus when he settled a dispute between the Christians and tavern-keepers.
The church underwent two restorations in the fifth and eighth centuries and in 1140-43 it was re-erected on its old foundations under Pope Innocent II.