A communication system based on fire signals was identified in Crete by the field archaeologist Nikos Panagiotakis, during an archaeological survey he conducted in the Pediada region in central Crete (from 1982 to 1989), covering more than 800 sq. km. The Pediada lies between the Bronze Age palatial sites of Knossos and Malia (from west to east) and extends south and southeast of modern Heraklion. The communication system was used during the Minoan period, especially between 1900-1700 BC. It worked by means of codified fire signals sent from the top of large, man-made constructions (in the shape of a truncated cone), built on the tops of hills or ridges. The network with its interconnecting visual contact could keep a close watch over, and so control natural passes and routes, covering the whole countryside and the coasts.