A photo of the Rocketdyne F-1 rocket engine -- "the most powerful single-nozzle liquid-fuelled rocket engine ever flown" -- being tested at the Marshall Space Flight Center, Alabama. Five of them powered the first stage of the Saturn V. Watch and listen to all of them being tested -- in Dolby 5.1 sound. It's amazing.
Here's a drone video of the S1C Test Stand that you can see in the video above:
And photo of the testing at the top of this article, watched from the other side.