Geomagnetic Poles (or Geomagnetic Fields as they are sometimes referred to) are mysterious poles located on the first floor of each stratum except for the first. They are automatically marked on the map. A geomagnetic pole allows the player warp back to town as well as save their game at that location. Once a geomagnetic pole is used from the labyrinth, the player is then allowed to warp back to that pole from town.
In Etrian Odyssey II, a different variant of Geomagnetic Pole can appear in the labyrinth, usually midway or near the end of a stratum. They are yellow unlike the standard purple, and the player cannot save their game there. These poles also can only bring a player into the labyrinth, not out, but they make trips into deeper parts of the labyrinth simpler. Only one of the yellow poles can be active at one time - activating one will disable all the others
In Etrian Odyssey III: The Drowned City, Geomagnetic Poles can also found during sea voyages in addition to the labyrinth. Activating a maritime Geomagnetic Pole unlocks them as staging points for future sea voyages, enabling much further exploration than simply starting from Armoroad.
In Etrian Odyssey Untold: The Millennium Girl, Geomagnetic Poles can also be found in Gladsheim after it has been connected to a Strata. This makes it for easier jumps directly to Gladsheim from Etria, or to Gladsheim from a certain Strata.