If I remember correctly in Arena there was a major city in Skyrim called Snowhawk? It was in some books and maps etc. Hasnt made it into Skyrim in any shape or form so can it be assumed this is another "Sutch" Case?

For Reference: http://images.wikia.com/elderscrolls/images/3/3c/TES_Map_Tamriel_Arena.jpg

Given the changes in city positions, snowhawk is probably in High Rock, if it still exists. Another thing to consider is that, in pre-skyrim maps, Markarth Side replaced Snowhawk's position as it exists relative to Solitude. And then for skyrim itself, Markath Side moved westward significantly.

Arena shouldn't really be considered a source of lore at this point. Snowhawk didn't appear in the PGEs, either, and though as DR mentioned Markarth seems to have replaced it.

As stated earlier, the map from Arena became obsolete around the time Morrowind hit the shelves. Assuming it was not simply retconned out of existence, centuries have passed since the events of Arena so it isn't a stretch that the city was destroyed or abandoned within that time frame.

There is actually a Fort Snowhawk you can go to, though I haven't been there myself.