Ever since archeologists unearthed a series of strange and spectacular artifacts from the Sanxingdui Ruins in China’s Sichuan province in 1986, there have been suspicions that this site may be otherworldly.

A number of bizarre bronze masks too big for humans, bronze heads decorated with gold foil, and other curiosities (including figurines with a suspicious resemblance to the modern Angry Birds game) have promoted fantasies that Sanxingdui was the remains of an alien civilization—or more reasonable suppositions that it is a previously unknown Bronze Age culture dating back 3,000 years ago. A new round of excavations, whose findings were presented to the public in March, may give further clues as to how this civilization rose and fell.