The giant pyramid containing the crystal skull is described by Major Carter to be "over 1000 meters tall" (approximately 3,300 feet tall). By modern-day comparison, the Burj Khalifa Tower in Dubai - the largest man-made structure ever built, stands at only 828 meters (2,717 feet) tall.
In the beginning, Carter says that there are leptons in the pyramid. In actuality, leptons are a type of subatomic particle. Several such particles include electrons, positrons, and neutrinos. However, in the case of neutrinos, they really do pass through everything no matter how dense. Sunlight is very rich in neutrinos. An estimated 65 million solar neutrinos pass through one square centimeter every second.
Quetzalcoatl is the Aztec god of wind, air and learning. He is also an important deity in a number of other Mesoamerican cultures including the Mayans and Incas, though he was most prominently worshiped by the Aztecs. The Aztecs believed that mankind was created by Quetzalcoatl, that he controlled the elements of air and wind and gave mankind the gifts of calendars and books, and that he taught their ancestors how to harvest maize (corn). Unlike most other Aztec gods, there seems to be little evidence to indicate that humans were sacrificed to Quetzalcoatl, while it was common practice to sacrifice children and young virgin girls to the other Aztec gods in order to appease them.
In real life, the crystal skulls discovered in Latin America have been found to be hoaxes. This included one found in the 1920s in Belize, the same location as the one that Daniel Jackson's grandfather discovered.
Daniel tosses his pack into the crevasse as he follows Teal'c down the stone path.