Many famous archaeological sites have been subjected to destructive fires,whether hostile or accidental, including Near Eastern cities constructedlargely of mud-brick. But how long did it take to burn down a city? Themud-bricks themselves provide a valuable record. By heating experimentalbricks of different sizes, shapes and compositions to high temperatures, theminimum duration of an ancient conflagration can be calculated. Theresulting equations were applied to bricks from the destruction of TelMegiddo at the end of the Iron Age I, and indicate that the burning lasted aminimum of two to three hours: a much shorter period than expected.