I ran some Spaceship Zero at the HPL Birthday Party gaming convention this past weekend and now Im making an effort to write the scenario up all nice-nice. It happens on Mars, so Im trying to figure out exactly where on Mars. The secret human base needs to be in a deep cavern, and Ive learned that Valles Marineris is a canyon similar to our own Grand Canyon, but ten times as long and seven times as deep and wide. Neat. Then I read about Noctis Labyrinthus, which apart from having a cool sounding name that literally means the labyrinth of night looks fantastic.
Heres a big shot of Mars showing Valles Marineris, which as you can see is ginormous. At the far left of the rift is Noctis Labyrinthus
But heres an actual photo from the Viking orbiter
And a fancy artistic rendition by Fahad Sulehria of novacelestia.com