In this place there are 5 unachievable golden buttons in pre-sealed dungeon. No notes of usage or clues. 4 are located in halls before boss, and one in the start changes from silver to golden, and stops working.
About golden buttons. This is supposed to be choose path puzzle, as Ignis and Prompto talk about pathes and Prompto says something like:" it's not important which path to choose as long as it leads to the treasure"