some 60 miles to the northwest. Like the Iraqw, they are known for their use of irrigation systems in agriculture. The Sonjo also maintain terraced village sites, albeit of considerably more rudimentary form than what is found at Engaruka. New studies have also revealed new information about the Middle Stone Age and Pastoral Neolithic occupational histories of the area. History of archaeological research The first European to record the existence of these ruins was Gustav Fischer, who passed them on July 5, 1883, and compared them to the tumbled-down walls of ancient castles. Scoeller and Kaiser mentioned the ruins of "Ngaruku" including great stone circles and dams in 1896-97. The first detailed and archaeological investigation was by Hans Reck, in 1913. Louis Leakey and Mary Leakey investigated the site in 1935, but were disappointed by the lack of burial sites. They estimated a population of 30,000, but this figure is now considered exaggerated. John Sutton of the British Institute in Eastern Africa later conducted excavations at Engaruka, and in 2002–2005 Ari Siiriainen led a research team from the Department of Archaeology at the University of Helsinki. In 2001-2004, studies were conducted by Daryl Stump of University College London as part of his PhD thesis work. In 2006, the University of Helsinki resumed Siiriainen's work, concentrating on the connections between Engaruka and the Sonjo area. Modern Engaruka Engaruka is also the name of a modern village not far from the archaeological site. The Maasai conduct tourist tours of the site. References See also Engaruka Collection of excerpts from different sources, by the nTZ, Northern Tanzania Information Resource Maps, Weather, and Airports for Engaruka, Tanzania, United Rep. of Weather graphs. Nurse, Derek & Franz Rottland. 1991. ‘Sonjo: Description, Classification, History’, in Sprache und Geschichte in Afrika, 12/13, 171-289. Westerberg, L.-O., Holmgren, K., Börjeson, L., Håkansson, N.T., Laulumaa, V., Ryner, M., and Öberg, H., 2010: The development of the ancient irrigation system at Engaruka, Northern Tanzania: Physical and societal factors. The Geographical Journal, doi: 10.1111/j.1475-4959.2010.00370.x Archaeological sites in Tanzania Former populated places in Tanzania Archaeological sites in Arusha Region Archaeological sites of Eastern Africa Archaeological history of Eastern Africa