Water levels in Europe’s major waterways have reached historic lows, sparking economic fears for the future and revealing unhappy echoes of the past.In Budapest, adjacent to the national parliament, the retreating waters of the Danube river have revealed a once-in-a-century discovery: the remains of two presumed German soldiers and a Wehrmacht DKW model military motorcycle.The city’s Institute and Museum of Military History said the vehicle was almost completely intact, preserved by Danube riverbed mud and engine diesel.Local historians say the dead men were probably killed during the Nazi occupation of the city from March 1944, possibly during the four-month Battle...