At the crossroads of the Plaza de las Plateras and the Plaza de la Quintana stands the Clock Tower, often known as the Trinity Tower or, less accurately, the Berenguela Tower. Some sources claim that building didn't continue when Archbishop Berenguel de Landoria took over, but the common belief is that it was begun in 1316 at the insistence of Archbishop Rodrigo de Padrón as a defense tower.61 Domingo de Andrade, who was appointed master builder of the cathedral, continued its construction and added two more storeys between 1676 and 1680. Using a variety of structures, he created a harmonious and ornamental ensemble, topping it all off with a pyramidal crown and a lantern (inside of which four incandescent lamps remain permanently lit). It reaches an altitude of 75 m.

Archbishop Rafael de Vélez commissioned clockmaker Andrés Antelo to construct and install a four-faced clock in the tower in 1833. The mechanism includes two bells, the larger of which marks the hours and is called the Berenguela, and the smaller of which marks the quarters; both bells were cast in 1729 by Güemes Sampedro; the Berenguela measures 255 centimeters in diameter and 215 centimeters in height and weighs about 9,600 kilograms; the quarter bell measures 147 centimeters in diameter and 150 centimeters in height and weighs about 1839 kilograms. Both bells were cracked, so Eijsbouts of Asten, the Netherlands, cast reproductions in 1989, and they were installed in the cathedral in February 1990.