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>
    <allimages aistart="2013-11-26T16:44:12Z" />
  </query-continue>
  <query>
    <allimages>
      <img name="Full_map_ex_1.png" timestamp="2013-11-29T18:51:17Z" user="AP" url="http://wiki.exploring-greece.gr/images/b/be/Full_map_ex_1.png" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Full_map_ex_1.png" ns="6" title="File:Full map ex 1.png" />
      <img name="Full_map_ex_4.png" timestamp="2013-11-29T18:43:52Z" user="AP" url="http://wiki.exploring-greece.gr/images/8/8c/Full_map_ex_4.png" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Full_map_ex_4.png" ns="6" title="File:Full map ex 4.png" />
      <img name="Full_map_ex_3.png" timestamp="2013-11-29T18:43:32Z" user="AP" url="http://wiki.exploring-greece.gr/images/c/c9/Full_map_ex_3.png" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Full_map_ex_3.png" ns="6" title="File:Full map ex 3.png" />
      <img name="Full_map_ex_2.png" timestamp="2013-11-29T18:43:14Z" user="AP" url="http://wiki.exploring-greece.gr/images/a/a1/Full_map_ex_2.png" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Full_map_ex_2.png" ns="6" title="File:Full map ex 2.png" />
      <img name="Full_map_dynamic_600h.jpg" timestamp="2013-11-29T18:42:23Z" user="AP" url="http://wiki.exploring-greece.gr/images/d/dc/Full_map_dynamic_600h.jpg" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Full_map_dynamic_600h.jpg" ns="6" title="File:Full map dynamic 600h.jpg" />
      <img name="Full_map_area_600h.jpg" timestamp="2013-11-29T18:42:04Z" user="AP" url="http://wiki.exploring-greece.gr/images/6/6a/Full_map_area_600h.jpg" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Full_map_area_600h.jpg" ns="6" title="File:Full map area 600h.jpg" />
      <img name="Start_page_annotated.jpg" timestamp="2013-11-28T16:30:18Z" user="AP" url="http://wiki.exploring-greece.gr/images/0/02/Start_page_annotated.jpg" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Start_page_annotated.jpg" ns="6" title="File:Start page annotated.jpg" />
      <img name="Show_tp_whole_annotated.jpg" timestamp="2013-11-28T16:28:45Z" user="AP" url="http://wiki.exploring-greece.gr/images/d/dc/Show_tp_whole_annotated.jpg" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Show_tp_whole_annotated.jpg" ns="6" title="File:Show tp whole annotated.jpg" />
      <img name="Related_places_reviews.jpg" timestamp="2013-11-26T16:51:08Z" user="AP" url="http://wiki.exploring-greece.gr/images/9/95/Related_places_reviews.jpg" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Related_places_reviews.jpg" ns="6" title="File:Related places reviews.jpg" />
      <img name="Other_data.jpg" timestamp="2013-11-26T16:47:30Z" user="AP" url="http://wiki.exploring-greece.gr/images/c/cb/Other_data.jpg" descriptionurl="http://wiki.exploring-greece.gr/index.php?title=File:Other_data.jpg" ns="6" title="File:Other data.jpg" />
    </allimages>
  </query>
</api>