Some amateur scholars believe that aliens built Machu Picchu. They find it difficult to believe that a people without iron tools, draught animals, or even the wheel could have lugged such large stones up the mountainside and built such magnificent structures. Archeologists and scholars agree, however, that the Incas, with their impressive engineering techniques and use of human labor, were more than capable of constructing the site without the assistance of outside (or otherworldly) forces.