Not quite sure if it is still the case, but not so long ago Germany was borrowing money at negative interest rate.
Edit: mea culpa. Looks like you're right : http://www.ft.com/cms/s/0/84a1ddc8-bce5-11e4-9902-00144feab7...
This happens not (only) because it is safer to keep piles of German bonds than piles of EUR, but because of the unorthodox ECB monetary policy. We certainly live in some very interesting times.