Caves and tunnels have always been part of human life. We've grown more adept at shaping these underground shelters and passages over the millennia, and today we dig for hundreds of reasons. We excavate to find both literal and cultural treasures, digging mines and unearthing archaeological discoveries. We use caverns for stable storage, for entertainment, and for an effective shelter from natural and man-made disasters. And as the planet's surface becomes ever more crowded, and national borders are closed, tunnels provide pathways for our vehicles and for smugglers of every kind. Collected below are some recent subterranean scenes from around the world.