A firebox is provided for use in a gas fireplace, the firebox comprising: a back which includes at least one combustion fan aperture, an upper end and a lower end and a length therebetween, a pair of sides, each side including an upper end, a lower end, a first riser which has an inner section and an outer section, the inner section attached to the back, a first flange, which is parallel to the back and extends outward from the back, and a second riser, wherein the outer section of the first riser, the first flange and the second riser extend above the upper end of the back and below the lower end of the back; a top which is attached to the inner section of the first risers and to the back at the upper end; and a base which is attached to the inner section of the first risers and to the back above the combustion fan aperture, to define an opening. The fireplace is also provided.