Higher Resolution Images

http://www.msss.com/moc_gallery/ab1_m04/maps/M0400291.gif

http://www.msss.com/moc_gallery/ab1_m04/nonmaps/M0400291.gif

We can speculate that Mars has underground cities and a tunnel system.
These tunnels can carry water from the poles and cargo throughout their world.

Early astronomers claiming to see canals on Mars may have actually witnessed
the
tunnel system under construction. The photo is actually of the Corinth Canal
in Greece that is six kilometers long.