the time of Spanish contact in the early 16th century may have been the descendants of the inhabitants of Calakmul. Modern history Calakmul was first reported by Cyrus Lundell in 1931. A year later he informed Sylvanus Morley of the site's existence and the presence of more than 60 stelae. Morley visited the ruins himself on behalf of the Carnegie Institution of Washington in 1932. In the 1930s surveys mapped the site core and recorded 103 stelae. Investigations stopped in 1938 and archaeologists did not return to the site until 1982 when William J. Folan directed a project on behalf of the Universidad Autónoma de Campeche, working at Calakmul until 1994. Calakmul is now the subject of a large-scale project of the National Institute of Anthropology and History (INAH) under the direction of Ramón Carrasco. Site description The site core of Calakmul covers an area of approximately , an area that contains the remains of roughly 1000 structures. The periphery occupied by smaller residential structures beyond the site core covers an area of more than within which archaeologists have mapped approximately 6250 structures. Calakmul matches the great city of Tikal in size and estimated population, although the density of the city appears to have been greater than that city. The stone used in construction at the site is a soft limestone. This has resulted in severe erosion of the site's sculpture. The city of Calakmul was built in a strongly concentric fashion and can be divided into zones as one moves outwards from the centre of the site. The innermost zone covers an area of approximately It contains most of the monumental architecture and has 975 mapped structures, about 300 of which are built from vaulted stone masonry. About 92 structures were built on large pyramids laid out around plazas and courtyards. The city's core was bordered on the north side by a high wall that controlled access from the north and may also have had a defensive function. Many commoners residences were built along the edge of El Laberinto swamp to the west of the site core, although some high-status residences and public buildings were interspersed among these. The area between the residences was used for horticulture. Water control The site is surrounded by an extensive network of canals and reservoirs. There are five major reservoirs, including the largest example in the Maya world, measuring . This reservoir is