The Saga prefectural government opened a sarcophagus on Monday that was unearthed at the Yoshinogari archaeological site in southwestern Japan and is preparing to study its contents.

Excavated from the enormous ruins of a moat-enclosed settlement in Saga Prefecture, the stone coffin is believed to have been built around the second to third centuries in the late Yayoi period during the time of the ancient country of Yamatai.

The coffin is around 2.3 meters long — bigger than other graves found at the site.