Apologies in advance for the crude MSPaint jobs.
In
Zelda II: The Adventure of Link, you must travel through a maze of caves which is called "Death Mountain". When you finish with this maze, you emerge into a small rectangular area to the south which has some interesting terrain and no discernible purpose. No dungeons or secret items appear here, except for the caves to the north where you acquire the hammer and the magic potion, which are called "Spectacle Rock" by some townspeople in the game.
Look familiar? Take a look at this overhead view of the map from the first Legend of Zelda game, and see if you notice any similarities:
This small area in Zelda 2 is obviously supposed to be an abbreviation of the map from Zelda 1. The cave in which you acquire the Hammer in Zelda 2 is the same cave where you rescued Zelda in Zelda 1.