Nintendo have dug up some of the original design documents that informed the 1986 NES classic, The Legend of Zelda. In the trailer above, you’ll see a gridded out view of the game’s overworld, as well as item and key placements.
There are also individual, detailed sketches of iconic rooms. Here are some from Takashi Tezuka, including the skull room.
Shigeru Miyamoto also lent his artistic talent, with this detailed, perspective drawing.
For a full look at some of the other docs, head over here.