Hellas basin occupies the northwestern part of the quadrangle and makes up the deepest depression on Mars and the largest, well-preserved impact structure, at ~2,300 km inner diameter. The basin floor, Hellas Planitia, is largely a hummocky plain, marked by a network of wrinkle ridges and patches of knobby and troughed terrains, including Hellas Chaos. The lowest elevation on the planet (–8,200 m) occurs within the 33-km-diameter Badwater crater in the northwest corner of the quadrangle in Hellas Planitia. The basin rim is partly dominated by plains and low shield structures to the south (Malea Planum and Amphitrites Patera) and northeast (the southern edge of Hesperia Planum in MC-22, and Hadriacus Mons). The plains lie at 0–3 km elevation. Slopes north of Malea Planum are furrowed by dense, shallow valley systems (including Axius and Mad Valles), whereas the northeastern slope is deeply dissected by Dao, Niger, Harmakhis, and Reull Valles. Except for Reull, these valleys have sinuous, trough-like rille forms, which narrow in the downstream direction. The Promethei Terra highlands, east of Hellas basin rim, are characterized by particularly rugged terrain, including high-standing massifs and deep crater forms.