If humans land on Mars by 2037 as NASA hopes, they'll need cities modeled on ones that already exist in extreme climates on Earth. Here are six high-tech (and a few low-tech) cities that would have a passing shot at survival in the Martian climate. Of course there are the obvious choices, like research stations in Antarctica. But there are other possibilities, like the instant city model developed at Black Rock City, home to arts festival Burning Man, which you can see here nestled in a Martian crater. And there are others potential Martian city models that might surprise you, like ones in Nunavut, Canada and in ancient Native American pueblos.