The world is full of abandon properties - Mostly human made structures, such as old buildings and other objects used at one time for the benefit of human civilization but now abandoned and no longer used. The original owner has longer deceased or disappeared. The government are left to deal with such eyesores. Buildings can be demolished or refurbished. They are relatively easy for the government to deal with. However , there is one kind of abandoned human structure that are difficult to find and expensive to rehabilitate. But if left untreated are dangerous to human environment. They are abandoned oil wells drilled deep into the underground. The oil companies that drill such well have long went out of business. What they left are many deep hole in the ground with a short crumbling iron structure above ground hidden by tall grasses. The dangers of such abandoned structures are not so much people/animal may accidentally fall in and die there but the exposed toxic materials left in such wells. The principal item is the emission of methane gas that are trapped below ground are now continuously polluting the atmosphere above ground and become the major contribution to global warming. Worse yet, they can contaminate fresh drinking water that humans use. Treatment cannot be simply put a cover over such used wells. They must be thoroughly cleaned, filled, and then covered up. This is an expensive proposition that the government must assume for everyone of such abandoned oil well. And there are thousands of such wells drilled, used, and abandoned over the 20th Century all over the world under different government waiting to be cared for. Till this problem is solved the entire human civilization of the world must suffer/endure the consequences!