Approaching the Cathedral Church of Durham from the north by the large open space between it and the Castle, known as the Palace Green, we obtain a complete elevation of the whole structure. There is little room to doubt, though the details naturally vary with the date of erection, that the original plan of Carileph's church has been carried out in its entirety, with two exceptions. These are the addition of the eastern transept or nine altar chapel at the east, and the Galilee or Lady Chapel at the west end. The entire length of the building, not including the Galilee chapel, is 431 feet, which is made up as follows:--Nine altar chapel 51 feet, the choir 120 feet, the transept 57 feet, and the nave 203 feet. The #Western Towers# are square and solid, and were evidently included in Carileph's own scheme, as the wall arcades on both the interior and exterior are carried round them. The Norman work is continued as far as the nave roof, and it is extremely probable that they were originally terminated at this height, in accordance with the Norman custom, with low pyramidal spires, probably of wood. Exactly at what date they were raised is not on record, but the style of architecture of the upper portion suggests the early part of the thirteenth century. The added portion, namely that above the clerestory, consists of four stages, and is beautifully varied by moulded arcading, with blind and open arches. The first and third stages have pointed arches, while those of the second and fourth are round. Above this again were tall wooden spires covered with lead. These were removed about the year 1657, and towards the close of the eighteenth century the present pinnacles and open parapets were added. At this time, also, much of the surface of the towers was renewed.