From the surface, El Castillo in Chichén Itzá is almost perfectly constructed. It sits at the centre of the plaza and rises into an excavation. Millions of tourists visit each year to see it and its famed equinox shadow, and their interest lies in its mathematical accuracy and iconic image. For years, the interest in this monument was largely limited to the physical structure that could be observed above ground.
However, as more research was done on the monument, the mystery only seemed to deepen.
