Castello, Giovanni Battista (jōvän`nē bät-tēs`tä kästĕl`lō), c.1509–c.1569, Italian painter and architect; called Il Bergamasco to distinguish him from Bernardo Castello, who also worked in Genoa. Giovanni was born near Bergamo, where many of his works still exist. After a trip to Rome he returned to Genoa, where he worked with Luca Cambiaso on the Palazzo Imperiale. Giovanni's propensity for grotesque decorations is best seen in the Palazzo Pallavicino (now the Palazzo Garega-Cataldi). In 1567 he went to Spain, where he became architect and painter to Philip II.