Sometimes just called the Frant's Tree (because of the archaeologist who discovered it), this ancient temple was built inside the largest tree on the continent (probably the tree that can be seen in the Morx Forest in Monster Rancher 3) when they were all still connected.
After the continental divide, it came to rest as part of Aurora Island. It is guarded by a powerful Dixie and is said to be a safe place for children.
In Monster Rancher Battle Card, you must go find Cox the explorer, who has gotten lost in the labrynth of the Frant's Ruins. Several plant-based monsters attack, but you must bring Cox back to his laboratory in Aurora.