Hlidskjalf

In Norse mythology, the Hliðskjálf (literally meaning the high seat with an expansive view) allowed Odin to see into all realms as well as listen to them.

[1] Although not explicit in any surviving source, there may be a connection between Hliðskjálf and the art of seiðr, a type of magic said to be practiced by Odin that was often performed from a high, raised platform called a seiðhjallr.

[2] In Grímnismál, Odin and Frigg are both sitting in Hliðskjálf when they see their foster sons Agnarr and Geirröðr, one living in a cave with a giantess and the other a king.

In Skírnismál, Freyr sneaks into Hliðskjálf when he looks into Jötunheimr and sees the beautiful giant maiden Gerðr, with whom he instantly falls in love.

In the first instance he seems to refer to it rather as a dwelling place: "There is one abode called Hliðskjálf, and when Allfather sat in the high seat there, he looked out over the whole world and saw every man's acts, and knew all things which he saw."