It is possible to draw polygons on your map. You can do this on a simple way: just provide the corner points as shown below.
API
<rd:map mapId="map_canvas" width="700px" height="500px" key="abcdefg" autoCenter="false" showDirections="false" onclick="" latitude="50.783363371066216" longitude="2.8255462646484375" zoomLevel="10"> <rd:polygon id="pol" strokeColor="#FF0000" strokeWeight="5" strokeOpacity="0.9" fillColor="#00FF00" fillOpacity="0.5" onclick="alert('clicked on ' + latlng);" clickable="true"> <rd:polygonPoint latitude="50.943704737090826" longitude="2.84820556640625" /> <rd:polygonPoint latitude="50.8059202661327" longitude="3.044586181640625" /> <rd:polygonPoint latitude="50.73296396507139" longitude="2.931976318359375" /> <rd:polygonPoint latitude="50.728617739899384" longitude="2.72186279296875" /> <rd:polygonPoint latitude="50.806788108266225" longitude="2.638092041015625" /> <rd:polygonPoint latitude="50.91167804783163" longitude="2.673797607421875" /> </rd:polygon> </rd:map>