"Curiosity," the nuke-powered, Mini Cooper-sized Mars rover, will aim for deep Gale crater.

via bbc.co.uk

Gale Crater is about 155km in diameter, and its lowest point is about 4.6km below datum, an imaginary "sea level"-type reference point on Mars from which all other elevations are measured.

Gale contains a central peak that should reveal stratigraphy ranging from Mars' wet period through the long drying out to the dessicated present.

http://www.bbc.co.uk/news/science-environment-14249524