The one that sang Lady of the Lake in the 70's? It was not Rainbow. This is a different band and different song. It was about 9 or 10 minutes long. It was prog rock and had a sound similar to Yes. Alot of keyboard melodies and catchy guitar riffs. I cant remember the name of the band, but I do remember the artwork on the record it was on. The artwork depicted a jewel-encrusted castle on a cloud hovering in the atmosphere. My dad used to have this album but it got lost years ago. I want to find out the name of the group so I can buy some of their albums