A complex composed of foundations has also recently been excavated in the palace area. Coded D17("No 17 palace"), it includes two groups of row-house-style buildings, both built on rammed earth terraces, according to Zhao.

The row-house building on the north side, for example, has five rooms on its facade. It is one room deep, and 40 meters wide in an east-west orientation, and covers an area of about 310 square meters.

"It's the widest single-row building in terms of facade found at the Erlitou site so far," Zhao says.

Before this discovery, archaeologists had wondered whether the area was a central square, and the layout of previously discovered ruins nearby also confused researchers.

Expanding work beyond Eritou per se sometimes helps demonstrate its core status. Other than the palace area, interesting discoveries were made last year at the Guchengcun site, which is across the river from the Erlitou core zone. Long considered an independent archaeological site, three newly unearthed moats and a rammed wall are now giving pause for thought.

The No 1 section of the moat spans over 1,700 meters. It is nearly 10 meters wide and 2 meters deep. The direction of No 2 and 3 moats parallel the main roads and ruins in Erlitou.

"They also embrace the Erlitou site from its north and east," Zhao says. "They probably functioned as the outer boundary of the city."

If this hypothesis is proved correct in follow-up research, it would mean that the Erlitou site was larger than 3 sq km in size.

"If so, the Erlitou site could be far larger than other archaeological ruins of its time in China," Wang says. "This would further demonstrate its core status in a state."

Only an area of 59,500 sq m has been excavated at Erlitou in the 60-some years since its discovery, and many questions await to be answered.

Construction of a new national-level archaeological research center focusing on the Xia and the following Shang Dynasty (c. 16th-11th century BC) began in September in Luoyang. It will be equipped with research labs, restoration facilities and warehouses for archaeological materials. It is expected to become a new hub for international cooperation on Xia-Shang studies.