Alternative interpretations Abydos helicopter: A pareidolia based on palimpsest carving in an ancient Egyptian temple. Dendera Lamps: Supposed to depict light bulbs, but made in Ptolemaic Egypt, debunked by the analysis of the epigraphic text. : a disc of notable precision apparently from ancient times in Saqqara. Its purpose is unknown. Iron Man (Eiserner Mann): An old iron pillar, said to be a unique oddity in Germany, but consistent with medieval methods of ironworking. Iron pillar of Delhi: A "rust-proof" iron pillar which supposedly demonstrates more advanced metallurgy than was available in India before 1000 CE. London Hammer: Also known as the "London Artifact", a hammer made of iron and wood that was found in London, Texas, in 1936. Part of the hammer is encased in "400-million-year-old" ("Ordovician era") rock. In 1985, anthropologist John R. Cole hypothesized that the stone surrounding the hammer is a historic carbonate soil concretion. Meister Print: A supposed human footprint from the Cambrian period, long before humans existed, which has been debunked as the result of a natural geologic process known as spall formation. Pacal's sarcophagus lid: Described by Erich von Däniken as a depiction of a spaceship. Piri Reis map: Several authors, and others such as Gavin Menzies and Charles Hapgood, have suggested that this map, compiled by the Turkish admiral Piri Reis, shows Antarctica long before it was discovered (cf. Terra Australis). Quimbaya airplanes: Golden objects found in Colombia and made by the Quimbaya civilization, which have been alleged to represent modern airplanes. In the Gold Museum, Bogotá, they are described as figures of birds and insects. Some of the artifacts have also been debunked as forgeries. Saqqara Bird: Supposedly depicts a glider, but made in Ancient Egypt. Shakōkidogū: Small humanoid and animal figurines made during the late Jōmon period (14,000–400 BCE) of prehistoric Japan, said to resemble extraterrestrial astronauts. Stone spheres of Costa Rica: Inaccurately described as being perfectly spherical, and therefore demonstrating greater stone-working skill in pre-Columbian times than has previously been known. Natural objects mistaken for artifacts Aix-en-Provence petrified tools: Likely petrified tree remains. Baigong pipes: Their natural origins have been challenged. Eltanin Antenna: Actually a sponge. Face on Mars: A pareidolia of a rock formation on Mars caused by the poor resolution of early orbital photography of the planet. Klerksdorp spheres: Actually pre-Cambrian concretions. Paluxy River tracks: Identified as giant humanoid footprints found alongside dinosaur tracks. Actually tracks of