The church we see on the grassy hill was built after Hernan Cortez and his Spanish army conquered Cholula one October day in 1519. The Spanish ravaged the Aztec holy city that day, murdering 10% of its population and burning down the many pyramids that dotted the area. But just underneath this church, buried for centuries, lay an ancient secret never discovered by the Spanish. It"s the largest pyramid in the world, the Great Pyramid of Cholula, so large its enormous base would span several Olympic-sized swimming pools.