The Sun and the Moon pyramids, built out of millions of adobe bricks are the largest pre-Columbian structures in South America. Interesting colored friezes have been discovered and can be seen at the Moon Pyramid. Large-scale human sacrifice at Huaca de la Luna became evident when archaeologists uncovered the remains of at least 34 sacrificed adult male individuals in the soft clay of the southeastern court, at the foot of the mountain. They had been bound, and judging by the type of wounds that had been inflicted, had probably been captured in battle. The sacrifice represents a single ritual event linked by archaeologist Steve Bourget to a season of torrential rains caused by an extreme case of the maritime El Niño phenomenon, which may have caused the final abandonment of this site.