Virtual Shuttle-Mir tour: Shuttle middeck

Here you see forward and right walls of the middeck.

Now look to the aft end of the Shuttle.
You see a big white construction with a hatch in it.
It's an airlock. Let's go there

Now you are in the airlock.
The next hatch leads to the tunnel extension
and further - to the Orbiter Docking System (ODS)