Where they meet every moon
This area is the lowest spot on the border it is half underground (on Desertclan side) desertclan will enter via a tunnel and Jungleclan enters through a break in the trees
The Jungleclan leader sits in an oak tree to address the clans while the Desertclan leader stands on the outcrop above where his clan enters which is surprisingly almost as high as where the Jungleclan leader sits in the tree
(I will announce let the leaders know when the first gathering will take place)