4 the site was thought to be a natural hill with 2500 year-old megalithic structures on top of it. But in 2010 geologist Dr Danny Hilman Natawidjaja (who earned his doctorate at Cal Tech) recognized this "hill" as a possible man-made pyramid and began to explore it using ground penetrating radar, seismic tomography, resistivity survey and other remote sensing techniques, as well as some direct excavations and deep core drilling.