A star-studded concert.

Check out Britney Spears making a virtual duet with Madonna in concert, all via a video she pre-taped specifically for the Material Mom's Sticky and Sweet tour! But the star sightings at Madonna's latest live extravaganza didn't end there.

Bono and Elton John were also spotted rocking out among the thousands of fans in Nice, France, says Britain's Daily Mail.

Sir Elton, who had a highly publicized falling out with Madonna some years ago, was seen "applauding enthusiastically" between songs, says the paper. Clearly the two stars have made up since!