The team is researching the origin of the rice. "If it was planted locally, it is valuable for us in relation to studies of the early agriculture on the Loess Plateau. If it came from somewhere else, we can infer there was probably a tribute system, involving transportation and trade," says Zhang Xiaoning.

The cultural relics are thought to be of a high level, which means they were used in rituals and sacrifices, instead of in daily life. "People who study civilizations have a consensus, that the early stage of a civilized society is a theocracy, and then it gradually evolves into a monarchal one. Therefore, sacrifice could help early leaders to strengthen their power, and became very important in early societies," says Han.

Other pieces of evidence that may support the theory that Nanzuo was a capital are red arrowheads made of stone and bone and covered with cinnabar. Western Zhou Dynasty (c. 11th century-771 BC) literature records show emperors at that time awarded feudal princes with red arrows, granting them the power to kill. The arrowheads found in Nanzuo may have had a similar function, symbolizing military power.

Nine giant terraces are formed around the core structure. One is on the central axis, and the other eight are distributed in a symmetrical way along the axis. "Each terrace covers more than 1,000 sq m," says Han.

The original height of the terrace is not clear, but the remaining part is three or four meters. "If it was a dozen meters high, with a smaller top, it would be like there were nine pyramids originally," he adds.