surveyed but unexcavated, estimated 4,000 BCE, layer beneath. Mnajdra and other Megalithic Temples of Malta, circa 3100 BCE and younger. Modern astronomical complexes Examples of modern astronomical complexes of stellar observatories include: The Leoncito Astronomical Complex in the San Juan Province of Argentina. The University of Idaho Astronomical Complex in the United States of America. The research and observational centre at the Instituto de Astrofísica de Canarias (IAC) and its observatories, the Observatorio del Roque de los Muchachos, on La Palma and the Observatorio del Teide, on Tenerife. The observatories of the Caltech Astronomy Department, California Institute of Technology in Pasadena, California, United States of America. References Burl, Aubrey., Prehistoric Astronomy and Ritual, Shire Archaeology, 2010 Archaeoastronomy Earth mysteries