drupal/core/themes/seven/templates/maintenance-page.html.twig

{#
/**
 * @file
 * Seven's theme implementation to display a single Drupal page while offline.
 *
 * All available variables are mirrored in page.html.twig.
 * Some may be blank but they are provided for consistency.
 *
 * @see template_preprocess_maintenance_page()
 */
#}
<div class="l-container">

  <header role="banner">
    {% if site_name or site_slogan %}
      <div class="name-and-slogan">
        {% if site_name %}
          <h1>{{ site_name }}</h1>
        {% endif %}
        {% if site_slogan %}
          <div class="site-slogan">{{ site_slogan }}</div>
        {% endif %}
      </div>{# /.name-and-slogan #}
    {% endif %}
  </header>

  {% if page.sidebar_first %}
    <aside class="l-sidebar-first" role="complementary">
      {{ page.sidebar_first }}
    </aside>{# /.l-sidebar-first #}
  {% endif %}

  <main role="main">
    {% if title %}
      <h1>{{ title }}</h1>
    {% endif %}
    {{ messages }}
    {{ page.content }}
  </main>

  {% if page.page_bottom %}
    <footer role="contentinfo">
      {{ page.page_bottom }}
    </footer>
  {% endif %}

</div>{# /.l-container #}