But not all is as it seems. Beneath the tiny church, hiding under tufts of grass, trees and soil, is an ancient pyramid of truly gigantic proportions. Standing 450 metres wide and 66 metres tall, from end to end the Great Pyramid of Cholula is equivalent to nine Olympic sized swimming pools.

For an obscure temple no one’s heard of, Cholula holds an impressive array of records: it’s the largest pyramid on the planet, with a base four times larger than the Great Pyramid at Giza and nearly twice the volume.

Never mind the largest pyramid – it’s the largest monument ever constructed anywhere, by any civilisation, to this day. To locals it’s aptly known as Tlachihualtepetl ("man-made mountain”). Thanks to the church on top, it’s also the oldest continuously occupied building on the continent.

The story goes that until the locals began construction of an insane asylum in 1910, nobody knew it was a pyramid. Certainly, by the time Cortéz and his men arrived, it was already a thousand years old and entirely concealed by vegetation.

Early excavations revealed a series of gruesome findings, including the deformed skulls of decapitated children.

Where did it come from? And why did it stay hidden for so long?