This podcast takes you on the hunt for hidden chambers within a pyramid in Mexico – potentially the resting place for the leaders of a mysterious pre-Colombian civilization. Physics World journalists James Dacey and Matin Durrani were the final visitors to a particle-physics detector located in a tunnel beneath the Pyramid of the Sun at the settlement of Teotihuacan, 50 km north-east of Mexico City. For the past 15 years, physicists have been using this experiment to track the flux of natural radiation and build an image of the pyramid’s sealed inner structure