Hellas Planitia is a plain located within the huge, roughly circular impact basin Hellas located in the southern hemisphere of the planet Mars. Hellas is the third or fourth largest impact crater and the largest visible impact crater known in the Solar System. The basin floor is about deep, deeper than the Moon's South Pole-Aitken basin, and extends about east to west. It is centered at Hellas Planitia is in the Hellas quadrangle and the Noachis quadrangle.