How do I Build rollercoasters underground in the game Roller Coaster Tycoon?

Answer 1

Which one? I think it was Rollercoaster Tycoon 3 where you couldn't build them underground at all.

In RCT1 and 2, you just have to have a height difference of 2 spaces to allow room for the tunnel to go from above to below ground level.

Answer 2

ya have to use the dirt tool and lower a section of the ground where your wanting to enter at as well as exit at, then build your your rollercoaster, etc towards the hole in the ground and then ya can start building the coasters underground..

I don't know if that makes much sense but it should give ya some kinda of idea of what to do..