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>
    <querypage qpoffset="10" />
  </query-continue>
  <query>
    <querypage name="Ancientpages">
      <results>
        <page value="20151201220354" timestamp="2015-12-01T22:03:54Z" ns="0" title="Memoria de la UPI 3" />
        <page value="20160225162311" timestamp="2016-02-25T16:23:11Z" ns="0" title="Nombre de la sede" />
        <page value="20160229180747" timestamp="2016-02-29T18:07:47Z" ns="0" title="UPI 4: Escuela Rural Santa Rosa" />
        <page value="20160229181409" timestamp="2016-02-29T18:14:09Z" ns="0" title="UPI 3: Escuela Rural Santa Rosa" />
        <page value="20160229194150" timestamp="2016-02-29T19:41:50Z" ns="0" title="UPI 5: Escuela Rural Santa Rosa" />
        <page value="20160229194559" timestamp="2016-02-29T19:45:59Z" ns="0" title="UPI 3: Escuela Rural San Miguel" />
        <page value="20160229194702" timestamp="2016-02-29T19:47:02Z" ns="0" title="UPI 4: Escuela Rural San Miguel" />
        <page value="20160229194811" timestamp="2016-02-29T19:48:11Z" ns="0" title="UPI 5: Escuela Rural San Miguel" />
        <page value="20160303001310" timestamp="2016-03-03T00:13:10Z" ns="0" title="UPI 5: Escuela Rural Capilla" />
        <page value="20160315124941" timestamp="2016-03-15T12:49:41Z" ns="0" title="Escuela Rural El Platanal" />
      </results>
    </querypage>
  </query>
</api>