In 1965, an expedition with an international composition that was not covered in the world community was organized, the purpose of which was to study the network of the previously not open temple complex of the Mayan civilization, presumably belonging to the preclassical era (2000 BC - 250 AD). The reason for organizing the expedition was declassified archival documents and devices obtained during other expeditions. But a year earlier, the first expedition was sent to that area, whose members no one else saw.