if entry has specific category, show specific html block

I have entries, which can have several categories.
These categories are in different categorie groups.

Now if i show an entry page, i want to display i certain html block
based on a specific category, the entry has or not.

i tried this, but its not working, i think i get the relatedTo thing wrong:

//i loop through all the categories in my group

{% for category in craft.categories.group('catGroup1') %}

//the i go to the section my entries are in and relate that to the categories i want to filter

{% set categoryListings = craft.entries({
  section: 'kelims',
  relatedTo: [
    { targetElement: category, field: 'filterThisCategory' }
  ]
}) %}

//if the entry has this category

{% if categoryListings|length %}

  display some html block

{% endif %}
{% endfor %}