I was playing a scenario and I noticed that there was a rollercoaster that ran underground, how do I do that if i want to custom build one like that? All help is greatly appreciated.

On the top right hand corner of the screen there is a little square with a picture of trees on it, to the very right of that is another thing you can click. I can't remember what it is but it allows you to raise or lower ground

build the roller coaster track slanted downward until it wont go anymore. then, use the land moving tool on the part of the ground where the new part would have been, to lower the ground one level. on the next consecutive square,lower the ground two levels. then u continue to build and it will go underground.