Selected areas are surrounded by a scrolling marquee border, like a line of marching ants. Units and structures within may periodically become aware of this border's presence. Valid building sites will appear blue or green. Invalid sites are red. Wait up to seven in-game days for your agents to complete the validation process, not accounting for travel time. IN THIS CAVERN: the diamond-studded ground is too rough for construction. Send round a man with a Sharp Axe or a Hammer. The finished space, properly cleared and districted, is suitable for fluid tanks, refining, or Light Hospital construction. Caution: the flickering fire itself is one of the Names of God.