Located near the entrance to the Ancient Ruins is a Female Explorer who was studying an important piece of Professor Hammerhead's Journal when she suddenly dropped it: The Translation Key. A gust of wind carried it to the top of the of the Ancient Ruins. In order to reach it, you must push a stone block to the right of the entrance to jump up to the vine from the large tree nearby; be careful, as the large tree drops oversize coconuts as obstacles that knock you down. Once you reach the wood platforms attached to the tree, jump to the left in order to gain access to the Ancient Ruins' Roof; here, you will find the Translation Key necessary to decipher the symbols of a locked door once inside.
It is possible to jump from the Stone Block to the vine from its default position, so you do not need to move it to begin with.