A ghost town is a town that has been abandoned, usually because the economic activity that supported it has failed. Old mining camps that have lost most of their population at some stage of their history, are sometimes included in the category, although they are active towns and cities today. Some ghost towns are tourist attractions, especially those that preserve interesting architecture. Visiting, writing about, and photographing them is a minor industry. Other ghost towns may be overgrown, difficult to access, or illegal to visit.