that's a trick of perspective
and atmospheric distortion.
The domed buildings are all a hazy, duplicating mirage of St Paul's cathedral in the distance
( HappyToast is dancing like Tim Booth on, Fri 2 Feb 2007, 14:04, archived)

makes sense
*wanders off, sucking bottom lip*
( mictoboy b3ta.com/questions/imagechallenge/post240894, Fri 2 Feb 2007, 14:06, archived)