WESTBROOK, Maine (AP) Think of it as a crop circle, but in a river.

A curious formation that has grabbed the attention of Greater Portland, Maine, is actually a spinning ice disk, and it’s roughly 100 yards wide. The formation in the Presumpscot River has gone viral on social media, and it has drawn comparisons to an alien spacecraft, a carousel and the moon.

Rob Mitchell, who owns a nearby office building, spotted the alien-looking disk Monday morning and immediately notified the city of Westbrook, just outside Portland. Officials say the disk is spinning slowly counter-clockwise, and has served as a big raft for ducks and other birds. ducks.

Mitchell says: “There were ducks sitting on it. The ducks were rotating on this big Lazy Susan. It was a big duck-go-round.”