Google Maps: display an encoded polyline

google.maps.geometry.encoding.decodePath(encodedPath:string)

http://code.google.com/apis/maps/documentation/javascript/reference.html#encoding

From that page:

var decodedPath = google.maps.geometry.encoding.decodePath(encodedPolyline);
var decodedLevels = decodeLevels(encodedLevels);

// Decode an encoded levels string into an array of levels.
function decodeLevels(encodedLevelsString) {
  var decodedLevels = [];

  for (var i = 0; i < encodedLevelsString.length; ++i) {
    var level = encodedLevelsString.charCodeAt(i) - 63;
    decodedLevels.push(level);
  }

  return decodedLevels;
}

Make sure the geometry libaray is being loaded per: http://code.google.com/apis/maps/documentation/javascript/basics.html#Libraries

Working example of the encoded polyline at: http://jsfiddle.net/ryanrolds/ukRsp/