The giant, perfectly circular area you’re referring to is indeed quite striking and often prompts imaginative explanations like alien activity. However, this circular shape is entirely man-made. It surrounds Mount Taranaki, an extinct stratovolcano in New Zealand, within a forest reserve whose borders were established by humans. The distinct boundary between the lush forest of the reserve and the surrounding farmlands creates this almost perfect circle visible from space. The reserve’s purpose is to protect the ecosystem around the volcano, and the contrast between the preserved forest and agricultural land results in the striking shape.