Yorkshire Wildlife Park on the bridge with lions on all sides probably about 8 of the 13 roaring at once - both spine tingling moments
The interesting thing about Lions roaring is each one seems to have to go through its complete roaring cycle-so they tend to start and stop at different times- the ones that join in later finishing last. I can remember watching them carefully in the old London Zoo LionHouse and seeing how the first one would stimulate the others to join in. Each lion ended with a series of grunts which gradually faded away to nothing-after the last one finished the SILENCE afterwards was almost as impressive.
Apparently the sound of Lions roaring travels something like 7 miles.