Philip appointed him architect-royal in 1559, and together they designed El Escorial as a monument to Spain's role as a center of the Christian world.
Juan Bautista je preživel večji del svoje kariere v Rimu, kjer je delal v baziliki svetega Petra in v Neaplju, kjer je služboval pri kraljevem podkralju, na čigar priporočilo je zbudil kraljevo pozornost.