Passage: The architecture is composed of seven pairs of triangular-shaped walls or prisms; the outermost pair being the shortest in height but widest in span, the inner pairs gradually change their aspect ratio and the innermost pair thus forms the peak point of the architecture. Each of these seven pairs of walls represents a significant chapter in the history of Bangladesh, namely the Language Movement in 1952, the Election of United Front in 1954, the Constitution Movement in 1956, the Education Movement in 1962, 6-point Movement in 1966, the Mass Uprising in 1969, and finally the climactic event of Liberation War in 1971, through which Bangladesh was liberated.

Question: How many pairs of triangular shaped walls is the architecture composed of?
seven