Can you dig it?

摘要

There are some trends that always seem set to continue. General elections will keep getting more depressing than inspiring. Hollywood will keep making superhero movies. And populations will keep moving from the country into cities. As the need to find room for urban working and living intensifies, it inevitably falls to engineers to think up solutions. In the 1920s, they built tall; and in some parts of the world they still do. Elsewhere, however, the pressures of city planning and sometimes unpleasant open-air environments are leading to an increasing interest in looking underground.