Click handlers for SVG polygons
You can use an array in a similar way here. Just leave the last one, as it doesn't fit the same pattern.

$.each(
  [
    { poly: 'p1', id: '#apla_p1' },
    { poly: 'p2', id: '#apla_p2' },
    { poly: 'p3', id: '#apla_p3' },
    { poly: 'p4', id: '#apla_p4' },
    { poly: 'a', id: '#apla_p5' },
    { poly: 'b', id: '#apla_p5' }
  ],
  function(o){
    var id = o.id; // copy to closure
    $('#pietra_svg #p1_4 polygon#' + o.poly).click(function() {
      $(id).fadeIn("slow");
      return false;
    });
  }
);

$('.close').click(function() {
  $('.apla').fadeOut("slow");
  return false;
});