Where is sendoff spring in Pokemon platinum?

It's near the middle of route 214, you'll see a bridge going half way over a small lake. Use rock climb to get to the entrance of turn back cave. if you have not defeated the Pokemon League the champion will be blocking the entrance of turn back cave. In the turn back cave, look for a portal that leads to the distortion world, behind it there is a rare bone that you can sell for a high price. Enter the portal to find the Griseous Orb, give it to your girantina to change it's forme, the orb will boost the power of ghost and dragon type moves.