This was the place in which the deliberations took place over whether to go to war against Saruman in consequence of the depredations of his Orcs. The Hobbits, Merry and Pippin, had been taken there by Treebeard and stayed nearby with Quickbeam during the three days of the meeting. The edge of the depression was lined with evergreens, but the bowl was empty except for a few birches that grew in the bottom. The name, 'derndingle', means 'hidden hollow' in an ancient language of Men in Middle-earth.
Portrayal in adaptations
In The Two Towers film Derndingle appears differently from how it is described in the novel. It is not so much a depression as a clearing within the forest (though as Ents arrive it can be seen that they are walking down a slope into the clearing). The edge is lined with trees that resemble oaks more than evergreens, and instead of birch trees within the space there is a single rock shaped like triangular pyramid.