Zone Visualization

Looking for a way to visualize an area that the player is meant to be able to passthrough in the air. I understand there are the Sphere zones, however they're rely on being close to another mesh to visualize. I was wonder if their might be a way to use the building plan meshes to create some sort of circle in the air?

um, colliders and ddraw?

how long do you want the box/sphere to be visible for?