Board Thread:Lore Discussion/@comment-139.218.211.126-20131213051049/@comment-3539474-20140211215339

There is a theory about the Snow Elves' ruins, Their buildings were constructed from enchanted ice or stalhrim, and after their disappeared the magic ran out; similiar to the descriptions of Alinor presented in PGE1. The Auri-El Temple in the Forgotten Vale, however, is made from more mundane matter, marble or moonstone.

This because Bethesda chose to focus on the Dwemer ruins/machines instead, despite them already having a game of their own in Morrowind. I think ignoring Falmer lore in favour of the Dwemer is one of Skyrim's lack of contents, and what little we got in Dawnguard DLC isn't enough to scoop that.