The red area indicates the <a href="https://en.wikipedia.org/wiki/Flemish_Diamond" class="extiw" title="en:Flemish Diamond">Flemish Diamond</a>, an metropolitan region.
<a href="//commons.wikimedia.org/wiki/User:SPQRobin" title="User:SPQRobin">SPQRobin</a>
Adapted from <a href="//commons.wikimedia.org/wiki/File:Be-map-nl.png" title="File:Be-map-nl.png">File:Be-map-nl.png</a>