What to See
The technical details here are truly spectacular. When you clap your hands in front of the Kukulkan Pyramid, the echo that comes back sounds exactly like the call of the quetzal, the sacred bird of the Maya. While some argue this is merely coincidence, my personal theory is that they discovered this acoustic phenomenon after construction and subsequently elevated the quetzal to sacred status because of it (this is my own speculation, not an established archaeological finding).
Even if the quetzal sound leaves room for doubt, the equinox light show seems entirely intentional. During each equinox, sunlight cascades down from the top of the pyramid to the bottom, illuminating the carved serpent head at the base in a slithering pattern. This alone demonstrates how remarkably advanced the Maya were in both engineering and astronomy. If these civilizations hadn't been completely destroyed, we might well be living in a very different era today.