Lions make many interesting sounds, but one of the most amazing to me is a male lion's roar. I have found them amazing ever since I heard Leo roaring from the MGM logo.
Even a recording of a male's roar sounds amazingly powerful, and it's not hard to believe that the roar can carry five miles. That takes a lot of energy. Roars are used for such things as defending territory and attracting mates and can even act to identify an individual. Males are highly territorial, and will often roar to try and keep rival males away. The roars are so deep and loud that they will vibrate the metal in the vehicles used to transport visitors to wildlife refuges.
Source is Smithsonian National Zoological Park.