I did the new’ish Out & Back loop last night which I enjoyed; decent length warm-up then up the volcano and the old KOM climb. Nice ride for an evening session, and my old legs do take some warming up so I like that before going up the climbs.
Just one question, is there a finish line? I’m assuming not, I did about 27/28 miles and didn’t see anything.
https://zwiftinsider.com/out-and-back-again/
Start/finish line is the sprint finish line which is a kind of arch made of rock with a white line on the road. Doesn’t look like a lot from what I remember, so would have been quite easy to miss if you were sure what you were looking for.
If you did 27/28 miles you have done the route and started it again. 
Cheers Ricky, I know the point you mean.