The architect faced several challenges. The new building had to fit an irregularly shaped, trapezoidal site; conform to the monumental scale of the Mall; and harmonize with John Russell Pope's classicizing West Building, completed in 1941. During the laborious design process, Pei and a small team of young architects explored many creative possibilities for the building's plan, exterior profile, and roofing of the great atrium. In a moment of insight, I. M. Pei solved the problem of the site's irregular shape by dividing it into an isosceles triangle and a smaller right triangle. Early in 1969, Pei's design was refined and elaborated to near-final form. The two triangles of the architect's original conception were pulled apart to create a slot that would emphasize the separateness of the two spaces: one for the museum's public functions and the other for its study center.