Solar Flare, Dragons, or Energy Weapons?

I have been looking into old ancient buildings for a bit and saw how quite a few structures possessed the characteristics of melted stone, rock, and mineral. I am sure most of you know what I am talking about. Some buildings look like an entire wax candle and some buildings look like they had been hit with a narrow and directed force. Could this be the result of a solar flare or something much more? I have been trying to figure it out but alas, dead end. I am stumped. What do you guys think? Could dragons possess such immense heat to melt buildings? Laser/energy weapons/technology? Greek fire of some sort? Or is it a solar flare?