Corrected entry: The predators use a high powered beam of energy (shown early in the film) to bore a hole down to the pyramid, yet the hole has a regular repeating groove pattern similar to what you would see from a drill bit. A laser would leave no such pattern.
Talon
22nd Aug 2004
Correction: The "beam of energy" was not necessarily a laser beam. There is any number of advanced alien devices that could achieve this effect including - but not limited to - a tiny pulse of antimatter, held in a modulated magnetic containment field, which is what would cause the grooves.