Paganini's No. 24 is considered a very difficult piece for a solo violin player. Below is a short segment of Hilary Hahn playing No. 24 at a 2007 music festival--just so you can get a taste of it--before we get to Rachmaninoff's Rhapsody.
Rachmaninoff's Rhapsody has 24 variations on Paganini's Caprice No. 24. By far, the most famous of these variations is No. 18, which is often played by itself. You have probably heard it many times in films and as part of other musical recordings. John Barry (known for the James Bond theme) won a Golden Globe nomination for his use of No. 18 in the 1980 film Somewhere in Time.
No. 18 is played slow and upside down. Instead of using Paganini's A minor, Rachmaninoff plays it in D flat major. Supposedly he immediately recognized the appeal this variation would have for audiences. Stories claim he quipped, "This one is for my agent."
I've had tickets to the Dallas Symphony for over twenty years. Last night I heard Stephen Hough play Rachmaninoff's Rhapsody--all 24 variations--in 23 minutes. It was simply glorious. The audience stood and cheered for several minutes afterward. I plan to go back either tonight or tomorrow afternoon to hear it again.
YouTube has Mikhail Pletnyov (or Pletnev) playing the entire Rhapsody over three videos. He begins the third video playing No. 18. You'll immediately recognize when it ends because Pletnyov looks to the orchestra and the tempo picks up as the 19th variation begins.