 The dominant feature of the building is the dome , which rises 25 @.@ 3 meters ( 83 ft ) from the ground , and has an outer diameter of 27 @.@ 7 meters ( 91 ft ) . The dome structure is layered , with an outer waterproofed casing of reinforced concrete 4 centimeters ( 2 @.@ 5 inches ) thick , and an inner concrete dome that is insulated by a layer of urethane foam . 
