More than worth its salt

The wider Yushan area has long been considered a major salt-producing hub. Evidence suggests production began as early as the Shang Dynasty (c.16th century-11th century BC) and continued into the 20th century. Salt mines, salt-making workshops and salt-transportation roads together form a Yushan site group centered on salt.

According to Wang Qing, a professor of archaeology at Shandong University, Zhongbao is currently Chongqing's only known aboveground salt production site dating to the Warring States Period, significantly enriching understanding of the region's early salt industry.

One of the site's most important discoveries is a remarkably well-preserved salt production workshop from the Warring States Period, complete with a salt stove, a brine-leaching pool and large quantities of pottery believed to be production waste, says Niu.

The centerpiece is an 8-meter-long, 1.2-meter-wide "dragon-shaped" salt stove — the first well-preserved example of its kind from the period found in China. Archaeologists found that its design made better use of heat, greatly improving production efficiency.

Iron remains recovered from the stove are believed to be salt-making tools. "The discovery shows pottery and iron vessels were used together in salt production," Niu says. "It provides physical evidence of the technological transition from ceramic to iron equipment."