Millie Hill bat cave

Iron Mountain, United States

Millie Hill bat cave (also known as Millie Mine bat cave) is an abandoned iron mine in Iron Mountain, Michigan that is now one of the largest bat breeding colonies in North America. The vertical mine shaft is blocked by a steel grate, which prevents entry by humans but allows bats to enter and exit freely. The bat cave is designated as an official Michigan Wildlife Viewing Area.

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Mine data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).

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