Like most of the structures here, the 40-metre- (120-foot-) high Treasury (named after legends of lost treasure) was hewn from the red sandstone valley sides.
The Treasury was cut from the sandstone in the valley side.  
mnli hypothesis: The Treasury was cut from the sandstone in the valley side.   premise: Like most of the structures here, the 40-metre- (120-foot-) high Treasury (named after legends of lost treasure) was hewn from the red sandstone valley sides.