The Great Tree (WoW)  

the fifth of the Great Trees can be found in Crystalsong Forest on the continent of Northrend. This tree is the only one in the forest that is not made of pure crystal and overlooks the northern edge of the zone. In fact, so massive is it that few of the trees even come close to its sheer size. The canopy of its branches rises several hundred feet in the air and its trunk is the thickness of a small castle in terms of girth. These Great Trees are known to be the portals into the Emerald Dream. Of them all, this tree is guarded endlessly by twelve green dragons, who nestle in the branches and stop any trespassers, save the serene druids, from entering.

Wrath of the Lich King required!