function initialize() {
  var map = new GMap2(document.getElementById("map_canvas"));
  map.setCenter(new GLatLng(19.400458,-99.168402), 16);
  map.setMapType(G_PHYSICAL_MAP);
  
  var point = new GLatLng(19.400458,-99.168402);
  map.addOverlay(new GMarker(point));
  }