Hadrian's wall now - fake, reconstruction, original?

Factual Questions
1

So last weekend I visited Hadrian’s Wall with a couple of friends. We walked a couple of miles of the wall, near Steel Rigg and Housesteads. Great fun and lovely scenery, but between the three of us we arrived at three different opinions about the wall itself:

  1. It’s pretty much a modern reconstruction.
  2. The stone is original, but the wall mostly collapsed / was plundered over the centuries and its current state is a result of repairs and reconstruction.
  3. There have been some repairs and some reconstruction, but much, or most, of the wall that remains is just as the Romans left it.

So what’s the Straight Dope? The wikipedia page, and most other pages I’ve read, could be interpreted to support any of the above (e.g. the preservation by John Clayton appears to support #1).

2

I’m not an expert on the wall but I think along the length of the wall you’ll find examples of all three. Some areas are completely original, some parts have been repaired, and there has been some modern reconstruction for the tourists.

3

I’ve got a Jackdaw on Hadrian’s Wall (which I’d love to visit sometime), and it supports Deeg – there is a lot of the original wall and ditch left, but portions have ben reconstructed to show you what it once looked like.