Unicorn Fountain

The is the fan-given name of an area resembling a fairy fountain seen in some of Ocarina of Time's pre-release material. This location does not exist in the completed game; it may be an earlier design of the fairy fountain or a different location altogether.

Theory
Though there is no known evidence to substantiate these rumors, many fans believe the entrance to the Unicorn Fountain was meant to be located under the ice in Zora's Domain as Adult Link. As it is impossible to melt the ice, the supposed entrance is unreachable by any normal means. However, it is still possible to find it in an alcove at the bottom of an underwater drop-off near the waterfall. It can be reached as both a child and an adult through various means, usually involving glitches or cheats. Using a glitch, it is even possible to get behind the wall that would have supposedly led to the fountain, despite there not being anything behind the wall.

It is also believed Link would receive the Sword Beam at the fountain.

Examining the geometry reveals that the alcove is not the right depth to serve as an exit, but it is entirely possible that at some point (before it was decided that Zora's Domain would remain perpetually frozen) it housed a treasure chest or some other reward not requiring a screen transition.