How do you build attractions underground in rollercoaster tycoon 1?

Answer 1

I haven't played the game in ages, but if my memory is correct you can only build very limited sections of rides underground. The best you can do is put some track underground (not the whole ride).

To do this, you'll need to make a sloping path going down enough for your track to travel through a flat wall of earth.

EARTH [||||||] <--------- TRACK

One there you can have some freedom with it. That's about all you can do though. Hope this helps.