Drag a builder to the shiny rock on the west side of the village and they will chisel the rock to create an idol. To speed up the process, drop more builders on the rock.
Through divine inspiration, your builders carved a large idol out of the sparkling, strange rock. It's as if the idol was always there, just waiting to be revealed.
If the idol is not yet carved, if you enter the map screen it will appear in the correct current state of rough rock, but if you click anywhere to zoom in, the idol will appear fully carved while the map fades.