Just found this site after many years of reading Larry Niven's work. As a motion graphics designer in London I've always wanted to visualise the Ringworld. Hope you like the links!
The Ringworld: http://www.youtube.com/watch?v=sR2296df-bc&feature=channel_video_title
Ring Walls & Spill mountains: http://www.youtube.com/watch?v=PJIwruvheLA&feature=channel_video_title
Great Fan site people!
PS: Apologies if i've listed this link in the wrong section....
The Voices of Fandom website: http://TVoF.info
The Voices of Fandom showcases, vintage and newly recorded, audio and video recordings of Fannish interest.