From Zelda Legends Wiki
A sign outside of the Wing Dungeon, the second dungeon of Oracle of Ages, describes it as the Ancient Cave.
This is the entrance of the Level 2 Dungeon called Wing Dungeon in the Oracle of Ages. If you try to get inside in the present time the cave will crumble immediately, because it is so old and fragile. This forces you to go back to the past to enter the cave then. The only problem is that the entrance is blocked and can only be opened by blasting your way in with the aid of a bomb. Unfortunately Link doesn’t have any bombs at that time. In order to get those you need to give some Mystery Seeds to Queen Ambi.
Sign outside the cave in the Present:
**Ancient Cave** Beware! Crumbles easily!
All translations are as close as they can be.