How to show contours on corridor?

Hi guys,

I am doing some training for some of my overseas colleagues, they are used to work in Civil3D, and I am telling them all how fantastic Powercivil is. Everything is going well until one of the students asks "how can I see the contours of my corridor, because I can do this in Civil3D?"

I cannot find an answer for her/them, and surely that cannot be correct. Does anyone have a clever idea? 

Thank you

Sadri