Excerpts from Books and Wikipedia
"Richard was returning to his kingdom after leading a crusader army in Palestine. Shipwrecked on the Croatian coast, he had decided to travel overland to Saxony. Unfortunately his route lay through the territory of his sworn enemy, Duke Leopold of Austria. . . . Leopold imprisoned Richard in Durnstein castle above the Danube, and put his captive up for auction to the highest bidder. He was sold to the Holy Roman Emperor Henry VI, who finally released him in February 1194 in return for a huge ransom of 150,000 marks, which his mother, Eleanor of Aquitaine, had to raise by taxing the English. Richard returned to a kingdom much weakened by his long absence." [1001 Days]