As the first example, I created a written sketch for the Water Temple from The Legend of Zelda: Ocarina of Time. Not because it's a level design masterpiece, but because it's probably one of the most controversial dungeons in the series.
There should be enough detail in the sketch to help brief the team and brainstorm on ideas. You could also start assembling lists of new assets and functionalities for artists and programmers. At the same time, we've left the majority of gameplay exploration to the grayboxing stage. The dungeons in this game are often sets of individual rooms and challenges that come together to fulfill a larger vision.
On a side note, I wonder if the makers of the original Ocarina of Time realized ...
