During The Legend of Zelda: Breath of the Wild's gameplay demos at E3, you can spot all sorts of ancient text on walls towers and more. However, fans on NeoGAF have discovered that the text can be translated into English, and have created a translation key for 24 out of 26 English letters. The messages vary, but many offer hints for how players should proceed or descriptions of the area they are entering; for example, text on a dungeon wall repeatedly spells out "DUNGEON," text on a large gear says "ROTATE," and text on a tower says "SHEAKTOWER."
It seems like Nintendo is even going to include some hidden jokes and memes in the game, as one translated set of runes says "NOW LOADING DO NOT TURN OFF ALL YOUR BASE ARE"; that last portion is clearly a reference to a horrible translation from the SEGA Mega Drive game Zero Wing, which went viral as a meme as early as 2000.
You can check out all of the currently-translated images in the gallery below, as well as a mockup of the game's language from Twitter user Ehm.