What is "breidablik"

In Norse mythology, Breiðablik (Broad-gleaming) is the home of Baldr. It is briefly described in Snorri Sturluson's Gylfaginning as one of the halls of Asgard:

"Then there is also in that place the abode called Breidablik, and there is not in heaven a fairer dwelling."

Later in the work, when Snorri describes Baldr, he gives a longer description, citing Grímnismál, though he does not name the poem:

"He dwells in the place called Breidablik, which is in heaven; in that place may nothing unclean be, even as is said here: Breidablik 't is called, | where Baldr has A hall made for himself: In that land | where I know lie Fewest baneful runes."

Breiðablik is not otherwise mentioned in the Eddic sources.