grammaticality - "such a day" or "such day"?

It's such a nice day today!

I'm interested in the usage of the indefinite article. I know this sentence is correct. We use an indefinite article in exclamations with countable nouns.

But the question is: If it's NOT an exclamation, what do we use? Let's say:

1. I went for a walk because it was such a wonderful day.


2. I went for a walk because it was a such wonderful day.


3. I went for a walk because it was such wonderful day.

Which variant is correct?

Answer

I went for a walk because it was such a wonderful day.

is correct.