Featured level suggestions

There are a selection of four levels which are featured at the top of the website, as well as visible from the main menu of the game. These have remained mostly the same for quite a long time now, so I am now making a thread to get suggestions for new featured levels.

I don't have any specific criteria for featured levels, but I would like them to be impressive, interesting, inspiring, neat eyecandy or all four of them. Basically anything that would show the strengths of Principia and would be a good idea to showcase for new players discovering Principia. Suggesting your own levels is fine too, if you believe that one of your own levels would be good to feature.