Jötunheim

Jötunheim ("Home of the Jötun") was the home of the Frost Giants and the Mountain Giants, called Jötun.

Jötunheim was located in Utgard, around Midgard and was surrounded by the sea.

Another assumption is that Utgard was located 'in' Jötunheim.

The world of the giants and the world of the gods (Asgard) was devided by the river Ifing.

Another abode of the giants was Gastropnir.

It was one of the "Nine Worlds", connected by Ygdrasil, located in the middle level.