It was mentioned that the underground passage runs under Feathered Serpent Temple, and the entrance is located a few meters away from the temple at the expected place, designedly sealed with large boulders nearly 2,000 years ago. The hole that had appeared during the 2003 storms was not the actual entrance. A vertical shaft, almost 5 meters wide, accesses the tunnel: it goes 14 meters deep, and the entrance leads to a nearly 100-meter-long corridor that ends in a series of underground galleries in the rock. After archaeologists broke ground at the entrance of the tunnel, a staircase and ladders (and later an elevator) were installed to allow easy access to the subterranean site. Work advanced at a slow and careful pace. Excavating was done manually, with spades. Nearly 1,000 tons of soil and debris were removed from the tunnel. The rich array of objects unearthed included: large spiral seashells, jaguar bones, pottery, fragments of human skin, wooden masks covered with inlaid rock jade and quartz, elaborate necklaces, rings, greenstone crocodile teeth and human figurines, crystals shaped into eyes, beetle wings arranged in a box, sculptures of jaguars, and hundreds of metallized spheres. The mysterious globes lay in both the north and south chambers. Ranging from 40 to 130 millimetres, the balls have a core of clay and are covered with a yellow jarosite formed by the oxidation of pyrite. According to George Cowgill from Arizona State University, "Pyrite was certainly used by the Teotihuacanos and other ancient Mesoamerican societies. Originally the spheres would have shone brilliantly. They are indeed unique, but I have no idea what they mean." All these artifacts were deposited deliberately and pointedly, as if in offering to appease the gods.