This is where the layout, at least the visible/modeled part of the layout begings and end. On the right is South Jackson yard, the eastern most modeled portion of the BC&SJ. On the left is Browning, the western most modeled portion of the layout.
Train come from and go to main staging by penetrating the backdrop. South Jackson has two holes in the backdrop, one for the mainline, the other for the yard's switching lead. Those holes will be covered (somewhat) by a highway overpass. Browning is more elegant, there's a tunnel portal.
On the far side the tracks converge at Toh Jct. (Toh stands for Top Of Helis). The panel in the sky shows how the Toh Jct. turnouts are set. The South Jackson station operator doubles as the Toh Junction towerman. A phone on the other side of the backdrop lets crews at the top of the helix call the tower to get passage through the Toh Jct. interlocking.