You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information.
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="Castellum_Fectio1.jpg|239" />
  </query-continue>
  <query>
    <pages>
      <page pageid="48" ns="4" title="Limes-wiki:In het nieuws" />
      <page pageid="209" ns="0" title="Romeinse muur Nijmegen Waalkade" />
      <page pageid="300" ns="0" title="Romeins schip: Millingse Liburna" />
      <page pageid="343" ns="0" title="Reizen langs de Limes" />
      <page pageid="431" ns="0" title="Limes et Laurium" />
      <page pageid="526" ns="0" title="Bataven" />
      <page pageid="544" ns="0" title="Romeinse drank: Wijn" />
    </pages>
  </query>
</api>