A nearly intact piece of ancient pottery likely more than 10,000 years old has been discovered on the floor of Lake Biwa in western Japan.

Researchers believe the artifact dates back to the early Jomon period, around 11,000 to 10,500 years ago, making it the oldest pottery found at the Tsuzuraozaki underwater archaeological site in Japan’s largest lake.

The discovery was made during an underwater survey carried out in October as part of a project commissioned by the Cultural Affairs Agency. An unmanned submersible fitted with four cameras captured photos and video at a depth of roughly 64 meters.

Using the collected images, the research team produced a 3D model of the lakebed, mapping its terrain and the placement of submerged relics. Through this analysis, they identified a 25-centimeter-tall pottery fragment shaped somewhat like an artillery shell.