diff --git a/core/modules/system/templates/radios.html.twig b/core/modules/system/templates/radios.html.twig
index bf38830..06c2210 100644
--- a/core/modules/system/templates/radios.html.twig
+++ b/core/modules/system/templates/radios.html.twig
@@ -12,4 +12,4 @@
  * @ingroup themeable
  */
 #}
-<div{{ attributes.addClass('form-radios') }}>{{ children }}</div>
+<div>{{ children }}</div>
diff --git a/core/modules/system/templates/region.html.twig b/core/modules/system/templates/region.html.twig
index b2c5471..7ff24de 100644
--- a/core/modules/system/templates/region.html.twig
+++ b/core/modules/system/templates/region.html.twig
@@ -21,7 +21,7 @@
   ]
 %}
 {% if content %}
-  <div{{ attributes.addClass(classes) }}>
+  <div>
     {{ content }}
   </div>
 {% endif %}
diff --git a/core/modules/system/templates/system-admin-index.html.twig b/core/modules/system/templates/system-admin-index.html.twig
index 17f8150..881700f 100644
--- a/core/modules/system/templates/system-admin-index.html.twig
+++ b/core/modules/system/templates/system-admin-index.html.twig
@@ -15,10 +15,10 @@
  * @ingroup themeable
  */
 #}
-<div class="admin clearfix">
+<div>
   {{ system_compact_link }}
   {% for position, blocks in containers %}
-    <div class="{{ position }} clearfix">
+    <div>
       {% for block in blocks %}
         {{ block }}
       {% endfor %}
diff --git a/core/themes/classy/templates/radios.html.twig b/core/themes/classy/templates/radios.html.twig
new file mode 100644
index 0000000..bf38830
--- /dev/null
+++ b/core/themes/classy/templates/radios.html.twig
@@ -0,0 +1,15 @@
+{#
+/**
+ * @file
+ * Default theme implementation for a 'radios' #type form element.
+ *
+ * Available variables
+ * - attributes: A list of HTML attributes for the wrapper element.
+ * - children: The rendered radios.
+ *
+ * @see template_preprocess_radios()
+ *
+ * @ingroup themeable
+ */
+#}
+<div{{ attributes.addClass('form-radios') }}>{{ children }}</div>
diff --git a/core/themes/classy/templates/region.html.twig b/core/themes/classy/templates/region.html.twig
new file mode 100644
index 0000000..b2c5471
--- /dev/null
+++ b/core/themes/classy/templates/region.html.twig
@@ -0,0 +1,27 @@
+{#
+/**
+ * @file
+ * Default theme implementation to display a region.
+ *
+ * Available variables:
+ * - content: The content for this region, typically blocks.
+ * - attributes: HTML attributes for the region div.
+ * - region: The name of the region variable as defined in the theme's
+ *   .info.yml file.
+ *
+ * @see template_preprocess_region()
+ *
+ * @ingroup themeable
+ */
+#}
+{%
+  set classes = [
+    'region',
+    'region-' ~ region|clean_class,
+  ]
+%}
+{% if content %}
+  <div{{ attributes.addClass(classes) }}>
+    {{ content }}
+  </div>
+{% endif %}
diff --git a/core/themes/classy/templates/system-admin-index.html.twig b/core/themes/classy/templates/system-admin-index.html.twig
new file mode 100644
index 0000000..17f8150
--- /dev/null
+++ b/core/themes/classy/templates/system-admin-index.html.twig
@@ -0,0 +1,27 @@
+{#
+/**
+ * @file
+ * Default theme implementation for the admin index page.
+ *
+ * Available variables:
+ * - system_compact_link: Themed link to toggle compact view.
+ * - containers: A list of administrative containers keyed by position: left or
+ *   right. Each container in the list contains:
+ *   - blocks: A list of administrative blocks, rendered
+ *     through admin-block.html.twig.
+ *
+ * @see template_preprocess_system_admin_index()
+ *
+ * @ingroup themeable
+ */
+#}
+<div class="admin clearfix">
+  {{ system_compact_link }}
+  {% for position, blocks in containers %}
+    <div class="{{ position }} clearfix">
+      {% for block in blocks %}
+        {{ block }}
+      {% endfor %}
+    </div>
+  {% endfor %}
+</div>