Hello,
I need to model the kind of walls that I show to you in the attached image. It have a circular section in the top. In this moment I resolve this with a 3D object, but sometimes I need to insert a window in the circular part, and that is imposible with a 3D object, I need a wall.

I have tried to do a reference plane, but I only can do to work with straight planes.

Do you know how to model it?