On May 6th, 1968, Pink Floyd performed at the Palazzo dello Sport, in Rome, Italy. I've seen two or three copies of this video on YouTube, but mine is in the highest quality, I believe. The others have cropped sides and bad audio quality, with quite blurry visuals that you'd only see in a 144p video.
Here's the infamous "Interstellar Overdrive", played by the post Syd Barrett Pink Floyd. David Gilmour played all of what Syd would usually play. The original version is 9 minutes and 40 seconds, and lives on "The Piper at the Gates of Dawn" album, released in 1967.
David Gilmour – guitar
Roger Waters – bass guitar
Rick Wright – organ
Nick Mason – drums