is there a way to get rollercoasters underground in RCT3

and if there is then i can recreate the london underground

It's automatic. Just point the track downward. It knows what to do. Eventually, you'll get to a depth where the surface remains intact, and you actually start building a tunnel.

In the scenery menu, you'll find something that looks something akin to a golf divot. Click on it. You'll find some "land blocks" that you can use to "fill in" the surface a bit. These vary in size, making smaller holes of the chasims that sweeping curves create when they dive underground or come up from down under.

For an interesting "On-ride" view, click on the glasses then the hilltop near the bottom of the menu. You can see through land. A ride on anything underground allows you to see whatever is above you like the ground was as transperant as the air, with a black background.

this is in the RCT3 (no expansions) mode?

where is the "akin to a golf divot"?

weird...

NO! It comes with an expansion. I have Platinum so it must come with either Wild! or Soaked!