The magnificent bigger-than-life Basilica Palladiana is not a church at all and was only partially designed by Palladio. Beneath it stood a Gothic-style Palazzo della Ragione (Law Courts and Assembly Hall) that Palladio was commissioned to convert to a High Renaissance style befitting a flourishing late- 16th-century city under Venice’s benevolent patronage.
http://www.officeoftourism.org/europe/italy/Veneto/vicenza.asp