In the middle of the 15th century, Juan de Colonia raised on these towers open pyramidal needles or spires with an octagonal base. Their fine fretwork definitely shaped the silhouette of the Burgos cathedral. He originated from Cologne (as Johan von Köln). His design matches the project of the Cologne Cathedral, which at that time only existed in drawings that he could have seen. The spires of the Cologne cathedral were only added much later. The spires of the Burgos cathedral were raised with the financial contributions of the bishop Alonso de Cartagena and of his successor at headquarters, Luis de Acuña, whose coats of arms, along with the Castilian-Leonese monarchy, appear in the parapets that connect to the tops of the towers. In these parapets master Juan also had the inscription pax vobis and the sculpture of Christ showing the footsteps of his Passion, in one, and the inscription ecce agnus dei and a sculpture of Saint John the Baptist, in the other.
