(Newser) – When Hernan Cortez and his Spanish army marched into Cholula in present-day Mexico nearly 500 years ago, they were greeted by a peaceful people prone to building pyramids instead of stockpiles of weapons. Those people and their pyramids fell, and fast, with 10% of the local population murdered in a day as their pyramids were torched into oblivion. But as legend has it, one mud-brick pyramid was hidden, perhaps accidentally by vegetation, and was for centuries mistaken for a mountain, until locals began to construct an insane asylum in 1910. That's when they discovered the largest monument ever...