<P> The marble capstone of the pyramidion is a truncated pyramid with a cubical keystone projecting from its base and a deep groove surrounding the keystone . The aluminum apex replaces its truncated top . The inside upper edges of the topmost slabs on the four faces of the pyramidion rest on the keystone and in the groove . It has a large vertical hole through which a 1.5 - inch (3.8 cm) threaded copper rod passes and screws into the base of the apex, which used to form part of its lightning protection system . The keystone and groove occupy so much of its base that only a small horizontal area near its outer edge remains . The weight of the capstone is transferred to both the inner and outer portions of the shiplap upper edges of the slabs . It weighs 3,300 pounds (1,500 kg), is 5 feet 2 inches (157 cm) high from its base to its top, and is 3 feet (91 cm) square at its base . </P> <P> The marble pyramidion has an extremely complex construction to save weight yet remain strong . Its surface slabs or panels are usually only 7 inches (18 cm) thick (with small thick and thin portions) and generally do not support the weight of slabs above them, instead transferring their own weight via 1 - foot (30 cm) wide internal marble ribs to the shaft's walls . The slabs are generally 7 feet (213 cm) wide and 4 feet 4 inches (132 cm) high with a 2 - inch (5 cm) vertical overlap (shiplap) to prevent water from entering the horizontal joints . Twelve such courses, the internal ribs, the marble capstone, and the aluminum apex comprise the pyramidion . Its height is 55 feet 0 inches (16.76 m). Its weight is 300 long tons (336 short tons; 305 tonnes). The slope of the walls of the pyramidion is 17 ° 24' from the vertical . There are twelve ribs, three per wall, which spring from the 470 - foot (143.3 m) level, all being integrated into the walls up to the 500 - foot (152.4 m) level . All are free standing above 500 feet, relying on mortise and tenon joints to attach neighboring stones . The eight corner ribs terminate six courses above the shaft, each corner rib resting on its neighboring corner rib via a miter joint, forming four corner arches . Each such arch supports a pair of square corner stones, one above the other totaling one course in height . Each corner rib is linked to the nearest center rib at the sixth course via a marble tie beam . The four center ribs terminate eight courses above the shaft at a marble cruciform (cross shaped) keystone, forming two main arches that cross each other . Two stones, each one course high, are mounted on each of the four ribs, supporting two additional courses above the cruciform keystone, leaving two courses to support the capstone's weight by themselves . </P> <P> The observation floor (nominally the 500 - foot level) is 499 feet 4 ⁄ inches (152.21 m) above the entry lobby floor or lowest landing level . It is 1 ⁄ inches (3.2 cm) above the marble base of the pyramidion and the top of the shaft walls . </P> <P> Four pairs of 3 - foot (91 cm) wide observation windows are provided, spaced 4 feet (122 cm) apart, inner stone edge to edge, all just above the lowest course of slabs (504 - foot level). Six are 1 foot 6 inches (46 cm) high while two on the east face are 2 feet (61 cm) high for easier egress . All were originally provided with thin marble shutters in a bronze frame each of which could be opened inward, one left and the other right per wall . After two people committed suicide by jumping through the open windows in the 1920s, hinged horizontal iron bars were added to them in 1929 . A ninth opening in a slab on the south face just below the capstone is provided for access to the outside of the pyramidion . It is covered by a stone slab which is internally removable . In 1931, four red aircraft warning lights were installed, one per face in one of its observation windows . Pilots complained that they could not be easily seen, so the monument was floodlit on all sides as well . In 1958, eight 14 - inch (36 cm) diameter holes for new red aircraft warning lights were bored, one above each window near the top edge of the fourth course of slabs (516 - foot level) in the pyramidion . In 1958 the observation windows were glazed with shatterproof glass . In 1974--76, they were glazed with bulletproof glass and the shutters removed . New bulletproof glass was installed during 1997--2000 . </P>

Is the washington monument taller than the statue of liberty