In Norse mythology, Valhalla is roofed by what?

In Norse mythology, Valhalla is a majestic, enormous hall located in Asgard, ruled over by the god Odin. Half of those who die in combat travel to Valhalla upon death, led by Valkyries to be with Odin, while the other half gets chosen by the goddess Freyja for the field Fólkvangr. In Valhalla, the dead warriors join the masses of those killed in combat (known as the Einherjar) and various legendary Germanic heroes and kings, as they prepare to aid Odin during the events of Ragnarök.

Ragnarök is a series of events, including a great battle, foretold to lead to the death of a number of great figures (including the gods Odin, Thor, Týr, Freyr, Heimdallr, and Loki), natural disasters and the submersion of the world in water. After these events, the world will resurface anew and fertile, the surviving and returning gods will meet and the world will be repopulated by two human survivors. Ragnarök is an important event in Norse mythology and has been the subject of scholarly discourse and theory in the history of Germanic studies.

Before the hall stands the golden tree Glasir, and the hall's ceiling is thatched with golden shields. Various creatures live around Valhalla, such as the stag Eikþyrnir and the goat Heiðrún, described as standing atop Valhalla and consuming the foliage of the tree Læraðr.