Researchers have uncovered a 1,700-year-old cemetery along part of the ancient Silk Road trade route that connected the Roman Empire and China.

Archaeologists found the cemetery in the city of Kucha in northwest China, and it included about 10 tombs which were excavated. Seven of them were large structures made out of brick, according to Discovery News.

Researchers found carvings of mythical creatures that respresent different seasons — the White Tiger of the West, Black Turtle of the North, Azure Dragon of the East, and Vermilion Bird of the South — in one of the tombs.

That particular tomb, which was labeled M3, included a burial mound with a ramp and a sealed gate, as well as a burial chamber and a side chamber.

The findings were published in the journal of Chinese Cultural Relics.

Scientists have known about the cemetery since July 2007, when the Xinjiang Institute of Cultural Relics and Archaeology excavated it with help from local authorities. The findings from that excavation were published in the Chinese journal Wenwu.

The large brick tombs were likely created for people who had a lot of money. However, researchers don’t know who is buried inside: robbers have cleared out some of its contents, and there is no writing to indicate the names of those buried or what positions they held.

Evidence suggests that the tombs had been reused several times, and some tombs had more than 10 occupants, according to the report. That fact alone merits further study, scientists say.

Kucha formerly held an important place 1,700 years ago. Control of the region was important for China’s rulers at the time due to its location on the Silk Road.

It was likely a powerful city-state that would have enabled control of trade routes in the Western Frontiers of China. There is an ancient saying that goes, “If you have Kucha, only one percent of the states in the Western Frontiers remain unsubmissive,” according to Discovery News.