A Jotun or Jötun in Norse mythology, is a giant. Groups of them are called Jötnar. Many are very large and strong; some are not. Sometimes however, gods and Jötnar would marry. The Frost giant's stronghold is called Utgardr and it is in Jötunheimr, the name for their realm. This is one of the nine Norse realms. Jötunheim is separated from Midgard, or Earth, by high mountains, and large forests. Outside their home world, giants seem to prefer to live in caves.