An unexpected treasure trove of sunken warships and prehistoric fossils have been uncovered by Europe’s record-breaking drought.Rivers have receded in the big dry sweeping across the continent, revealing relics long thought lost.WATCH THE VIDEO ABOVE: Europe’s drought reveals Nazi warships and mammoth fossilsKnow the news with the 7NEWS app: Download today ArrowOn the drying Danube riverbed in Serbia lies a historian’s boon. In 1944, Nazis fleeing the Red Army scuttled the ships but severe drought means today it’s water that’s retreating, revealing the sunken fleet.Patrol boats, torpedo boats and transport ferries have been exposed, abandoned in what’s now modern-day Serbia...