Asgard is the main Realm of the Norse Pantheon. The halls of Odin, Frigga, Thor, Sif, Vidar, Hermod, Magni, Modi, Aegir, Baldur, and Forseti are here, and Asgard is the secondary realm of Loki, Frey, Freya, Idun, Bragi, and Tyr.
It is located in the first Layer of Ysgard and the name is occasionally used to describe the entire layer. It connects to a variety of planes via The World Ash, Yggdrasil, a Planar Path that Asgard sits at the top of. It is connected to the Prime Material Plane by the rainbow-hued Bifrost bridge.
Sources
Planes of Chaos, pages 111-113
Manual of the Planes (1st edition), page 96
On Hallowed Ground, page 140, map on pages 144-145
Deities & Demigods (3rd edition), page 165
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