London (CNN) -- Coal slag heaps up to 450-feet high may not seem the obvious candidates to join a list that includes the pyramids of Egypt, the Great Wall of China, and Yellowstone National Park.

CNN: Coal slag heaps join pyramids on World Heritage list

Apparently, American cultural insensitivity was also on display, as Spalding recounts how in Egypt, U.S. ball players used one of the Great Pyramids for a backstop and photographed themselves atop the Sphinx, much to the chagrin of locals.

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