A clever experiment is taking place under the Pyramid of the Sun in Teotihuacan, Mexico.

Artuto Menchaca is installing a cosmic ray detector in an ancient tunnel directly beneath the pyramid. If there is variation in the number of muons getting through from different directions, that will inidicate different densities and quite possibly a secret chamber. Once pin-pointed it could be excavated!

The results should be available mid-2004. A similar project he undertook found no evidence of chambers in the Pyramid of Kephren in Egypt.

More information in the July 26 2003 edition of New Scientist, or via the link below (translated from Spanish by Google).