In a day or two I'll get around to uploading some photos of Iizuka, Japan, a former coal-mining town in the center of Fukuoka prefecture.
The low con-shaped mountain on the left of this picture is a slag heap. The locals call it the Mt. Fuji of Iizuka (I think they're all delusional). Incidentally, if you look up "slag heap" on Wikipedia then go to the Japanese page, you'll find some pictures of Iizuka's famed slag heap.
I walked around this old pile of rock and dirt the other day and was surprised to discover how large it was--nearly as big around the base as the Great Pyramid of Giza (approx. 1600 m). There's wasn't much to see from up close, unfortunately.
As I made my way around the mountain, I couldn't help but wonder what remained below ground if all that rock and dirt, plus coal had been dug up. How long will it be before the earth collapses in on itself and swallows up Iizuka like the town of Macondo in Gabriel García Márquez's One Hundred Years of Solitude.