If you want to feel a little of the wonder that medieval peasants must have felt when they walked into Chartres or Salisbury cathedrals for the first time, get yourself down to the Turbine Hall of Tate Modern. The Danish artist Olafur Eliasson has created one of the most mesmerising pieces of large-scale art ever seen on these shores - a sun rising out of a sweet-scented Wagnerian mist that sets the hairs on the back of your neck tingling.