Icelandic Wonders

In taking the quiz below, one of the multiple choice answers was the following word:

Miðbæjarmiðnæturrúnturinn

I have no clue what it means, but I am in awe of it.

[Maybe Kristin can help me out here - although the mystery of it is also pretty cool]

If my site here weren't called Xoloitzquintle already, maybe I would call it that. Heehee.