Back in the days of the NES, memory was scant and needed to be conserved whereever possible. With that in mind, Takashi Tezuka designed the dungeon maps for the original The Legend of Zelda game in the following conservational manner. After playing the game several times over the course of 20 years, I still needed to have it pointed out to me.
The dungeon maps, in order, color-coded for recognition:
And now, in their designed arrangement:
Modeled after the images shown at http://www.nintendo.co.uk/NOE/en_GB/news/iwata/iwata_asks_-_zelda_handheld_history_15603_15604.html#top
There were only going to be 9 dungeons, originally, but in his design, Tezuka accidentally only used half the available memory. The design team decided to make a second quest and use the remaining memory in the next 9 dungeons.