Did a highly advanced civilisation exist in prehistory? Is the Giza Pyramid a remnant of their technology? Then what was the power source that fueled such a civilisation? The technology of harmonic resonance claims renowned master craftsman and engineer Christopher Dunn. In a brilliant piece of reverse engineering based on twenty years of research Dunn reveals that the Great Pyramid of Giza was actually a large acoustical device! By its size and dimensions this crystal edifice created a harmonic resonance with the Earth and converted Earth's vibrational energies to microwave radiation. The author shows how the pyramid's numerous chambers and passageways were positioned with deliberate precision to maximise its acoustical qualities. This may be the same technology discovered by Nikola Tesla and the solution to our own clean energy needs.