Concrete will succumb to high enough temperatures and is only fire retardant. Ever read fairy tales of witches living in glass castles? This is a reference to real technology. The formulae hasn't been successfully duplicated, but many ancient fortress were literally fused or welded into one continuous face by superheating the stones for greater strength. California fought a hard fight to eliminate the shake cedar rooftop, mandate brush clearance and promote fire retardant landscapeing. What nobody can stop is 'development' on scale with the cancer cell in ever farther and often difficult areas to reach, a finite water resource system farther behind than the much lamented gasoline refineries doubly crippled by extended drought conditions. I watched the canadian Superscoopers pass overhead making near tree level drops. There are 3 in the whole world with a 4th hanger queen for parts. We get them from Oct to Dec. The local enterprise out of Van Nuys Airport offering 'Mile High Club' flights for couples owns 4 planes and is considering adding a 5th.