two manufactured materials were of great importance in roman architecture: concrete and fired clay in the form of structural bricks and tiles, and to a lesser extent, in architectural decoration. these materials were used in buildings all over the roman empire, and in many areas, they fell out of use again after the roman period, only to be rediscovered centuries later. like other mass-produced roman ceramic objects, bricks and tiles were often marked with inscriptions that indicate their manufacturer, or the organisation or authority, military or civilian, for which they had been made.