Super Smash Bros. producer Masahiro Sakurai posted a set of screenshots for the 3DS version today, detailing one of the Mario-themed levels.
As with the past Super Smash Bros. titles, there will be dynamic levels, which'll scroll from side to side with varying landscapes and platforms. One of these, featured in the 3DS edition, will be called "Super Mario 3D Land", according to Sakurai. It'll feature side-scrolling, venturing into a valley, going downhill and continuing on rails to the end pipe to return to the beginning - taking around two minutes per lap.
What other franchises would you like to see turn side-scrolling in the next Super Smash Bros. games?