Earth's omphalos (navel) Picture
This rock is supposed to be the navel of Mother Earth and the center of the world. Delphi, Greece.
The site of Delphi was believed to be determined by Zeus when he sought to find the centre of Grandmother Earth (or Gaia). He sent two eagles flying from the eastern and western extremities, and the path of the eagles crossed over Delphi where the omphalos, or navel of Gaia was found.