Strata: Worldwide

Crafted at least 3,500 years ago, this mysterious piece is widely considered one of the greatest objects from Papua New Guinea. Known as the Ambum Stone—named for its discovery in the Ambum Valley—not much is certain about this en-igmatic sculpture, including what is depicted. While the animal does resemble a baby echidna, differences can be seen on the sculpture, including a ridge running up the center of the head and down to the shoulders and a “belt” below the belly. Believed to be used for ritual purposes, it is possible the stone doesn’t represent a real animal at all, but rather an ancestral being, such as the Rainbow Serpent.

Standing about 8 inches tall, the Ambum Stone was carved from tough lava stone with stone tools in a process that likely took weeks or even months. Since the sculpture’s surface layer contains a large amount of calcium, the stone may have spent a significant amount of time—possibly thousands of years—in the limestone caves near the valley.

This puzzling piece can be found at the National Gallery of Australia, Canberra.