When you stare at it, you'll think it looks fast and it's not even moving just sitting in the stand. Then you'll start to wonder how fast you could go on it. Probably beat all your mates and then clock Strava.....
The first thing you'll notice is the lack of cables showing, that's because they are all internal because external cables aren't aero. Then you'll notice up by the head tube on the down tube, that there is a little hatch with a wheel in it. This is when you'll turn it a few times and ask "what does this wheel do?" No stress most of the staff did the same thing when we saw it too.
Since all the cables are hidden it makes it hard to add cable tension to the front derailleur, this wheel is barrel adjuster and will add cable tension. Also, if you want Di2 on your Madone, the whole hatch can come out and be replaced with a door that will hold the battery and cables, making them all hidden.
This is just one of many features of the Trek Madone 9.5 and you can see it (maybe even test ride it) at Kiwivelo Wellington.