Large holes were then bored into the sides of the skulls and placed onto a large wooden pole prior to being placed in the tzompantli - a towering rack of skulls in the front of the temple.

Two columns of decorative mortar skulls were placed either side of the real ones to honour the gods and scare off potential enemies.

Paintings and written descriptions from the early colonial period have long documented the macabre site. One historical report claimed one rack contained more than 130,000 real skulls.