Edit in JSFiddle

Result
JavaScript
HTML
CSS

var createMap = function() {
  /* global itowns,document,GuiTools*/
  const positionOnGlobe = {
    longitude: 2.3465,
    latitude: 48.88,
    altitude: 25000000
  };

  // iTowns namespace defined here
  const viewerDiv = document.getElementById('viewerDiv');
  const globeView = new itowns.GlobeViewExtended(viewerDiv, positionOnGlobe);

  globeView.listen(itowns.GlobeViewExtended.EVENTS.GLOBE_INITIALIZED, () => {
  
    //adds mousePosition widget
    mousePosition = new itowns.control.MousePosition({
      collapsed: false
    });
    globeView.addWidget(mousePosition);
    
  });

  var orthoLayer = new itowns.layer.GeoportalWMTS({
    layer: "ORTHOIMAGERY.ORTHOPHOTOS"
  });

  globeView.addLayer(orthoLayer);

}

Gp.Services.getConfig({
  apiKey: "ortho,altimetrie",
  timeOut: 20000,
  onSuccess: createMap
});

var infoDiv = document.getElementById("info");
infoDiv.innerHTML = "<p> Extension iTowns version " + Gp.itownsExtVersion + " (" + Gp.itownsExtDate + ")</p>";

<body>
  <div id="viewerDiv">
    <button id="tiltButton">
      jsFiddle bug - click on this text to activate tilt (ctrl + left click)
      <br>
      Do not integrate this button to your own non-jsFiddle pages
    </button>
  </div>
  <div id="info"></div>
</body>

html {
  height: 100%;
}

body {
  margin: 0;
  overflow: hidden;
  height: 100%;
}

#viewerDiv {
  margin: auto auto;
  width: 100%;
  height: 400px;
  padding: 0;
}

#tiltButton {
  background-color: white;
  position: absolute;
  top: 20px;
  left: 50px;
}

#info {
  padding: 5px;
  width: 100%;
  height: 20px;
  font-family: "monospace";
  font-size: 10px;
}