LOS Rings

From AgeofWiki

This option apparently is intended to show the LOS of objects in the Editor.

Its major purpose is to allow scenario designers to determine whether objectives, landmarks, and hidden areas are visible to the player's units and buildings before they are supposed to be revealed. This way the designer can control the pace and flow of exploration in a scenario and provide appropriate space for hidden areas, objectives, and special landmarks to remain hidden as needed.

As with Toggle Range Rings, it appears to not work in the Editor.