Yggdrasill is the base of the Norse God Cyborgs, located somewhere in the mountains of Scandinavia. It is based on the legendary tree of life from Norse Mythology.
It resembles a giant mistletoe tree, but its internal structure is a man-made metal fortress with a network of pneumatic air elevators and a lava moat outside surrounding the area near its roots.
After his defeat by the Cyborgs and before his death, Odin activated the self-destruct mechanism in the hopes of killing them, however they escaped before the tree collapsed into a pile of rubble