Melas Chasma
Melas Chasma is a canyon on Mars, the widest segment of the Valles Marineris canyon system, and thought to be an ideal site for a human colony given that it has the highest air pressure of any site on the planet, and may also have water in abundance.
It is located east of Ius Chasma at 9.8°S, 283.6°E in Coprates quadrangle.