From abandoned asylums to cursed castles, these are the most haunted places on Earth where centuries of tragedy, mystery, and ...

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 ...

Sustainable Earth: Cities. Rio+20 shows how our rapidly urbanizing world presents challenges and opportunities for sustainable development.