For the first century of its existence, the church's interior was modestly decorated. However, in the 1660s, Grand Master Raphael Cotoner ordered the redecoration of the interior so as to rival the churches of Rome. Calabrian artist Mattia Preti was in charge of the embellishment, and effectively completely transformed the interior in the Baroque style. The annexes on the side of the cathedral were added later and feature the coat of arms of Grand Master António Manoel de Vilhena who reigned from 1722 to 1736.