First, the Nazis, then, the Soviet Union - shortly after World War Two - dumped tens of thousands of tonnes of chemical weapons 70m to 120m down in the Baltic Sea, near the Danish island of Bornholm.
Navigation equipment at the time was not very good and the Soviet Union did not record the exact locations, so the precise spots are unknown.
The old munitions have also drifted from place to place over the decades, with bombs in wooden crates sometimes washing up on Danish and Swe...
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Already a member? Login hereAndrew Rettman is EUobserver's foreign editor, writing about foreign and security issues since 2005. He is Polish, but grew up in the UK, and lives in Brussels. He has also written for The Guardian, The Times of London, and Intelligence Online.