simplest way of constructing curved polygon(3d)?

[totaljj]

I need to make a humpbacked bridge in opengl
I can make it by specifying many points and using gl_polygon but there must be better way of doing it.
I prefer rather simple method as the bridge is a simple one.

[Reedbeta]

Google for Bezier curves and NURBS. These are mathematical objects that let you construct curved surfaces from a few control points, however, they aren't really going to be simple if you've never seen them before.