The enormity of the Great Pyramid poses a challenge for any who would attempt to explain how it could have been constructed. It is estimated to comprise some 2.4 million stone blocks averaging 2.5 tons (2.27 metric tons) each, plus additional blocks weighing considerably more lying deep within the pyramid where they serve special functions. Its height when new, 480.9 feet (146 m), would have been within 74 feet (21.3 m) of the top, 555 feet (169.7 m), of the Washington Monument in Washington, DC, which was built 4,444 years later. The average weight of the blocks used in the pyramid and the monument is roughly the same, but the Great Pyramid comprises roughly 65 times as many blocks as the Washington Monument.