Proximities of Ma'adim Vallis (Natural Colors; credits: ESA)

Caption ESA:"Mars Express image of a Region close to Ma’adim Vallis, one of the largest - after Vallis Marineris - canyons on Mars.
The imaged Region lies South-East of Ma’adim Vallis; the pictures are centred at about 29° South Lat. and 182° East Long. and have a ground resolution of 15 mt/pixel.

Ma’adim Vallis is located between the Volcanic Province of Tharsis, which harbours 4 volcanoes, including the largest in the Solar System, and the Hellas Planitia Impact Basin.
The canyon, approx. 20 Km wide and 2 Km deep, originates in the Southern Highlands close to the so-called ‘Dichotomy Boundary’ and ends in Gusev Crater.
The Dichotomy Boundary is a narrow Region separating the cratered Highlands, located mostly in the Southern Hemisphere of Mars, from the Northern Hemisphere's Lowland Plains".