<P> The cathedral is some 574 feet (175 m) in length (including the portico of the Great West Door), of which 223 feet (68 m) is the nave and 167 feet (51 m) is the choir . The width of the nave is 121 feet (37 m) and across the transepts is 246 feet (75 m). The cathedral is slightly shorter but somewhat wider than Old St Paul's . </P> <P> The main internal space of the cathedral is that under the central dome which extends the full width of the nave and aisles . The dome is supported on pendentives rising between eight arches spanning the nave, choir, transepts, and aisles . The eight piers that carry them are not evenly spaced . Wren has maintained an appearance of eight equal spans by inserting segmental arches to carry galleries across the ends of the aisles, and has extended the mouldings of the upper arch to appear equal to the wider arches . </P> <P> Above the keystones of the arches, at 99 feet (30 m) above the floor and 112 feet (34 m) wide, runs a cornice which supports the Whispering Gallery so called because of its acoustic properties: a whisper or low murmur against its wall at any point is audible to a listener with an ear held to the wall at any other point around the gallery . It is reached by 259 steps from ground level . </P> <P> The dome is raised on a tall drum surrounded by pilasters and pierced with windows in groups of three, separated by eight gilded niches containing statues, and repeating the pattern of the peristyle on the exterior . the dome rises above a gilded cornice at 173 feet (53 m) to a height of 214 feet (65 m). Its painted decoration by Sir James Thornhill shows eight scenes from the life of St Paul set in illusionistic architecture which continues the forms of the eight niches of the drum . At the apex of the dome is an oculus inspired by that of the Pantheon in Rome . Through this hole can be seen the decorated inner surface of the cone which supports the lantern . This upper space is lit by the light wells in the outer dome and openings in the brick cone . Engravings of Thornhill's paintings were published in 1720 . </P>

How many steps to the top of st pauls cathedral