Castello was born 1558 in Gandino near Bergamo. He was an architect, sculptor and as well as painter. Castello was called "il Bergamasco" to distinguish him from the other painter. In cooperation with Bernardino Cantone he built the Palazzo Doria Spinola. He died 1578 in Madrid.
Important works by Giovanni Battista Castello
- The decoration of Lanzi Palace at Gorlago
- Chapel for the Duomo di San Lorenzo
- Palazzo Doria Spinola
- Palazzo Carrega-Cataldi (Camera die Commercio di Genova)
- Palazzo Carrega-Cataldi (Camera die Commercio di Genova), gilded Room