South when Shook and Kidder published their report on Mound E-III-3, a "Miraflores" mound and the largest known thus far from the site, and which contained seven structures built onion-skin fashion over and around each other through time. Two extraordinarily rich royal tombs were found within the edifices, probably representing consecutive rulers during the "Miraflores" Preclassic apogee of Kaminaljuyu. In the early 1950s Heinrich Berlin excavated a large mound in the ancient Preclassic core of the city. In the 1960s Pennsylvania State University undertook extensive excavations at Kaminaljuyu, under the direction of William T. Sanders and Joseph W. Michels. The processualist and unilineal cultural evolutionary theoretical orientation of the Penn State project were in sharp contrast to the Carnegie work before and to the historical, cultural-historical, sometimes epigraphy- and art-historically driven paradigm of Lowland Maya research after. In the 1990s, Marion Popenoe de Hatch and Juan Antonio Valdés conducted excavations in the southern districts of the site, and a Japanese team investigated a large mound near the modern archaeological park. Emphases since the 1970s on Classic Maya hieroglyphic texts and discoveries of great sites in the northern Petén turned attention away from the SMA, and a long period ensued during which proponents of a Maya Lowlands origins for Maya civilization held sway. More recently, the debate was rejoined with discoveries along the southern Pacific coast of Mexico and in Guatemala that greatly antedate developments in the Lowlands. Occupation history The known parts of Kaminaljuyu lie on a broad plain beneath roughly the western third of modern Guatemala City. Soils are rich because of frequent volcanic eruptions; volcanic ash in the form of hardened tuff reaches depths of several hundred meters in and around Kaminaljuyu, and deep clefts or barrancos mark the landscape. There are many mysteries, in addition to size and scale, that likely will remain unanswered about Kaminaljuyu. These questions are mainly about the role of the city as the greatest of the Southern Maya area (SMA) in Preclassic times, particularly during the Miraflores period, c. 400–100 BC. The SMA is long believed to have been seminal in the development of Maya civilization. Arévalo and Las Charcas cultures Kidder, Jennings, and Shook referred to Kaminaljuyu's artifacts as representative of what they called a "Middle Culture" which they believed represented the earliest phase of complex social and cultural development in Mesoamerica. This reflected their conclusion about the great antiquity of