function initialize() {
  var map = new GMap2(document.getElementById("map_canvas"));
  var center = new GLatLng(51.476687, -0.384645);
  map.setCenter(center, 15);
  var marker = new GMarker(center);
  map.addControl(new GSmallMapControl());
  map.addControl(new GMapTypeControl());
  map.addOverlay(marker);
  var myLayer = new GLayer("org.wikipedia.en");
    map.addOverlay(myLayer);
}