Ísland farsælda frón is set to the famous poem Ísland (Iceland) by Jónas Hallgrímsson. The poem was published in 1835; I haven’t been able to find out who created the music (click the link above for a detailed translation and discussion).
Voces Thules (0:47)
The Voces Thules version was my first encounter with this piece.
This last version is really fun, wacky and out there. The band has little or no internet presence and may no longer exist.