Valles Marineris is a huge rift valley on Mars, a canyon system dwarfing the Grand Canyon on Earth. A portion of it, Melas Chasma, is featured in new images from the Mars Express spacecraft. In this spot, the canyon is about 9 kilometres (5.6 miles) deep, and sulphate deposits are evidence of a former lake. There are also other water-cut channels in the immediate vicinity. There are additional and larger images, including 3D perspectives, here.
Perhaps the proposed Martian airplane will fly over this area for even better views…?