This spring is located underground near the Underground Medical Lab. It is used to help researchers find new ways to heal. Rumors are that once you set foot in this spring your health will be restored. But the sacrifice for that is that 1/9 of your life will be cut away from you.
No one under the rank of Jounin can enter, Jounins may enter with signed form from Kage allowing permission. If you are caught here you must direct yourself to the KazeKage office. Ranks over Jounin are allowed, but no messing around. There will be consequences if these rules are not followed.