This video created by NASA’s Science Visualization Studio zooms in on an area on Mars where water flowed abundantly into the delta of a once great river.  (Link via io9) :

This is a Great Zoom into the so-called Distributary Fan on Mars. It is located just northeast of Holden Crater. As seen from Martian orbit by the Mars Orbiter Camera (MOC) flying on the Mars Global Surveyor (MGS) spacecraft, this dramatic visualization shows us where liquid water likely flowed across the Martian surface sometime in the planet’s past.