<svg xmlns='http://www.w3.org/2000/svg'>
<g transform="translate(30,30)">
  <!-- transform-origin specifies a point relative to the top left of the
       element's paint bbox when transform-box is set to 'fill-box'
  -->
  <rect x='10' y='10' width='100' height='100' fill='blue'
        style="transform:rotate(90deg); transform-origin:0px 100px;
               transform-box:fill-box;"/>
</g>
</svg>