Sweden's coral reefs

I bet you didn't know that Sweden has coral reefs.

Well, they aren't alive -- they are fossil coral reefs that grew over 400 million years ago, when Sweden and the rest of Scandinavia were closer to the equator. These old corals now lie in the Baltic, and make up the island of Gotland.

I recently wrote about visiting Gotland from a geologist's perspective for the magazine Earth:
http://www.earthmagazine.org/article/travels-geology-gotland-getaway-swedens-tropical-escape-baltic