The Mainline run is now a terrain park zone that is roped off.
There is usually a half pipe, with several jumps and features.
On skiers right when coming from Siberia Ridge Line, there is usually a nice groomer that works it's way back to the Gold Coast area.
Don't duck the ropes to enter the terrain park, only enter at the top.
Mainline is named for an old chairlift that used to be in this area.