How to float a div over Google Maps?

Try this:

<style>
   #wrapper { position: relative; }
   #over_map { position: absolute; top: 10px; left: 10px; z-index: 99; }
</style>

<div id="wrapper">
   <div id="google_map">

   </div>

   <div id="over_map">

   </div>
</div>

#floating-panel {
  position: absolute;
  top: 10px;
  left: 25%;
  z-index: 5;
  background-color: #fff;
  padding: 5px;
  border: 1px solid #999;
  text-align: center;
  font-family: 'Roboto','sans-serif';
  line-height: 30px;
  padding-left: 10px;
}

Just need to move the map below this box. Work to me.

From Google

Just set the position of the div and you may have to set the z-index.

ex.

div#map-div {
    position: absolute;
    left: 10px;
    top: 10px;
}
div#cover-div {
    position:absolute;
    left:10px;
    top: 10px;
    z-index:3;
}