diff --git a/Documentation/ProjectFile/gml/c_gml.md b/Documentation/ProjectFile/gml/c_gml.md
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..5be1f4301818a8ee0e8a77a2bffadaadc225c572 100644
--- a/Documentation/ProjectFile/gml/c_gml.md
+++ b/Documentation/ProjectFile/gml/c_gml.md
@@ -0,0 +1,3 @@
+In gml files geometries, i.e., points, polylines, and triangulated surfaces, are
+defined.
+These geometries can be used in project files, e.g., to set boundary conditions.
diff --git a/Documentation/ProjectFile/gml/points/i_points.md b/Documentation/ProjectFile/gml/points/i_points.md
index 576add64edccf5d980a0ff86143dc43a7109a788..629d0f80d62297021f7ef1fe8c8359a08213b090 100644
--- a/Documentation/ProjectFile/gml/points/i_points.md
+++ b/Documentation/ProjectFile/gml/points/i_points.md
@@ -1 +1 @@
-\ogs_missing_documentation
+Contains point definitions.
diff --git a/Documentation/ProjectFile/gml/points/point/a_id.md b/Documentation/ProjectFile/gml/points/point/a_id.md
index 576add64edccf5d980a0ff86143dc43a7109a788..74338bd51db3200b824be139741d63c395157e21 100644
--- a/Documentation/ProjectFile/gml/points/point/a_id.md
+++ b/Documentation/ProjectFile/gml/points/point/a_id.md
@@ -1 +1,2 @@
-\ogs_missing_documentation
+ID of the point. It is used to reference this point in the definition of
+surfaces or polylines.
diff --git a/Documentation/ProjectFile/gml/points/point/a_name.md b/Documentation/ProjectFile/gml/points/point/a_name.md
index 576add64edccf5d980a0ff86143dc43a7109a788..4ea3bfb2f386023102eb1832f766a465febb6209 100644
--- a/Documentation/ProjectFile/gml/points/point/a_name.md
+++ b/Documentation/ProjectFile/gml/points/point/a_name.md
@@ -1 +1 @@
-\ogs_missing_documentation
+Name of the point. It is used to reference the point in the project file.
diff --git a/Documentation/ProjectFile/gml/points/point/a_x.md b/Documentation/ProjectFile/gml/points/point/a_x.md
index 576add64edccf5d980a0ff86143dc43a7109a788..41f914254138da8520afe7ba41d3c2d3e0f80597 100644
--- a/Documentation/ProjectFile/gml/points/point/a_x.md
+++ b/Documentation/ProjectFile/gml/points/point/a_x.md
@@ -1 +1 @@
-\ogs_missing_documentation
+x-coordinate of the point.
diff --git a/Documentation/ProjectFile/gml/points/point/a_y.md b/Documentation/ProjectFile/gml/points/point/a_y.md
index 576add64edccf5d980a0ff86143dc43a7109a788..0b12fa75be6464e4c2c5cda672aebdd48224525a 100644
--- a/Documentation/ProjectFile/gml/points/point/a_y.md
+++ b/Documentation/ProjectFile/gml/points/point/a_y.md
@@ -1 +1 @@
-\ogs_missing_documentation
+y-coordinate of the point.
diff --git a/Documentation/ProjectFile/gml/points/point/a_z.md b/Documentation/ProjectFile/gml/points/point/a_z.md
index 576add64edccf5d980a0ff86143dc43a7109a788..923fdb82ff0c4d7bacba64b30ee5677d3723bd68 100644
--- a/Documentation/ProjectFile/gml/points/point/a_z.md
+++ b/Documentation/ProjectFile/gml/points/point/a_z.md
@@ -1 +1 @@
-\ogs_missing_documentation
+z-coordinate of the point.
diff --git a/Documentation/ProjectFile/gml/points/point/i_point.md b/Documentation/ProjectFile/gml/points/point/i_point.md
index 576add64edccf5d980a0ff86143dc43a7109a788..9b00fe3f018e8dac9c22e4ffae7d41e1d8347c75 100644
--- a/Documentation/ProjectFile/gml/points/point/i_point.md
+++ b/Documentation/ProjectFile/gml/points/point/i_point.md
@@ -1 +1 @@
-\ogs_missing_documentation
+Defines a single point.
diff --git a/Documentation/ProjectFile/gml/polylines/i_polylines.md b/Documentation/ProjectFile/gml/polylines/i_polylines.md
index 576add64edccf5d980a0ff86143dc43a7109a788..e9929013937e32ccdbb2fee696f9f1ba057bf1e9 100644
--- a/Documentation/ProjectFile/gml/polylines/i_polylines.md
+++ b/Documentation/ProjectFile/gml/polylines/i_polylines.md
@@ -1 +1 @@
-\ogs_missing_documentation
+Contains polyline definitions.
diff --git a/Documentation/ProjectFile/gml/polylines/polyline/a_id.md b/Documentation/ProjectFile/gml/polylines/polyline/a_id.md
index 576add64edccf5d980a0ff86143dc43a7109a788..7cd2fd8c1ba2824559b6a904484c0fe472e39ddb 100644
--- a/Documentation/ProjectFile/gml/polylines/polyline/a_id.md
+++ b/Documentation/ProjectFile/gml/polylines/polyline/a_id.md
@@ -1 +1 @@
-\ogs_missing_documentation
+ID of the polyline. Currently unused.
diff --git a/Documentation/ProjectFile/gml/polylines/polyline/a_name.md b/Documentation/ProjectFile/gml/polylines/polyline/a_name.md
index 576add64edccf5d980a0ff86143dc43a7109a788..2abacdde47ed57ec3b96307548fbcdb206729713 100644
--- a/Documentation/ProjectFile/gml/polylines/polyline/a_name.md
+++ b/Documentation/ProjectFile/gml/polylines/polyline/a_name.md
@@ -1 +1 @@
-\ogs_missing_documentation
+Name of the polyline. Used to reference it in the project file, i.e., for instance to set boundary conditions.
diff --git a/Documentation/ProjectFile/gml/polylines/polyline/i_polyline.md b/Documentation/ProjectFile/gml/polylines/polyline/i_polyline.md
index 576add64edccf5d980a0ff86143dc43a7109a788..70af4a01b0b54be349d310e50e57666b6a21d5e4 100644
--- a/Documentation/ProjectFile/gml/polylines/polyline/i_polyline.md
+++ b/Documentation/ProjectFile/gml/polylines/polyline/i_polyline.md
@@ -1 +1,3 @@
-\ogs_missing_documentation
+Defines a single polyline.
+A polyline is a sequence of line segments, which is given here by a list of
+points; two adjacent points define one line segment.
diff --git a/Documentation/ProjectFile/gml/polylines/polyline/t_pnt.md b/Documentation/ProjectFile/gml/polylines/polyline/t_pnt.md
index 576add64edccf5d980a0ff86143dc43a7109a788..67c9e4b4331e90fafcc5de492a32f332ff6db963 100644
--- a/Documentation/ProjectFile/gml/polylines/polyline/t_pnt.md
+++ b/Documentation/ProjectFile/gml/polylines/polyline/t_pnt.md
@@ -1 +1,2 @@
-\ogs_missing_documentation
+References a \ref ogs_file_param__gml__points__point "point".
+The content of this tag is the respective \ref ogs_file_attr__gml__points__point__id "point ID".
diff --git a/Documentation/ProjectFile/gml/surfaces/i_surfaces.md b/Documentation/ProjectFile/gml/surfaces/i_surfaces.md
index 576add64edccf5d980a0ff86143dc43a7109a788..f58852866191168b68fe738c47d6044a5bd76f3a 100644
--- a/Documentation/ProjectFile/gml/surfaces/i_surfaces.md
+++ b/Documentation/ProjectFile/gml/surfaces/i_surfaces.md
@@ -1 +1 @@
-\ogs_missing_documentation
+Contains surface definitions.
diff --git a/Documentation/ProjectFile/gml/surfaces/surface/a_id.md b/Documentation/ProjectFile/gml/surfaces/surface/a_id.md
index 576add64edccf5d980a0ff86143dc43a7109a788..ddc80ae99472fb79b1ce8f3d7427cabf52fd637f 100644
--- a/Documentation/ProjectFile/gml/surfaces/surface/a_id.md
+++ b/Documentation/ProjectFile/gml/surfaces/surface/a_id.md
@@ -1 +1 @@
-\ogs_missing_documentation
+ID of the surface. Currently unused.
diff --git a/Documentation/ProjectFile/gml/surfaces/surface/a_name.md b/Documentation/ProjectFile/gml/surfaces/surface/a_name.md
index 576add64edccf5d980a0ff86143dc43a7109a788..a7ed0f2097b1ccd4e9e643ffec0d1c1d3f009549 100644
--- a/Documentation/ProjectFile/gml/surfaces/surface/a_name.md
+++ b/Documentation/ProjectFile/gml/surfaces/surface/a_name.md
@@ -1 +1 @@
-\ogs_missing_documentation
+The name of the surface. Used to reference it in the project file, i.e., for instance to set boundary conditions.
diff --git a/Documentation/ProjectFile/gml/surfaces/surface/element/a_p1.md b/Documentation/ProjectFile/gml/surfaces/surface/element/a_p1.md
index 576add64edccf5d980a0ff86143dc43a7109a788..4c7cabdcf9f8ac883b55e29a6624f0b8dcb09ac9 100644
--- a/Documentation/ProjectFile/gml/surfaces/surface/element/a_p1.md
+++ b/Documentation/ProjectFile/gml/surfaces/surface/element/a_p1.md
@@ -1 +1,2 @@
-\ogs_missing_documentation
+The first triangle point.
+This attribute references a \ref ogs_file_attr__gml__points__point__id "point ID".
diff --git a/Documentation/ProjectFile/gml/surfaces/surface/element/a_p2.md b/Documentation/ProjectFile/gml/surfaces/surface/element/a_p2.md
index 576add64edccf5d980a0ff86143dc43a7109a788..e35a3d28700571231e26225454cd941ee3cc3c09 100644
--- a/Documentation/ProjectFile/gml/surfaces/surface/element/a_p2.md
+++ b/Documentation/ProjectFile/gml/surfaces/surface/element/a_p2.md
@@ -1 +1,2 @@
-\ogs_missing_documentation
+The second triangle point.
+This attribute references a \ref ogs_file_attr__gml__points__point__id "point ID".
diff --git a/Documentation/ProjectFile/gml/surfaces/surface/element/a_p3.md b/Documentation/ProjectFile/gml/surfaces/surface/element/a_p3.md
index 576add64edccf5d980a0ff86143dc43a7109a788..447b818b8d31f2bd2baaf801c107d59e5ed883f3 100644
--- a/Documentation/ProjectFile/gml/surfaces/surface/element/a_p3.md
+++ b/Documentation/ProjectFile/gml/surfaces/surface/element/a_p3.md
@@ -1 +1,2 @@
-\ogs_missing_documentation
+The third triangle point.
+This attribute references a \ref ogs_file_attr__gml__points__point__id "point ID".
diff --git a/Documentation/ProjectFile/gml/surfaces/surface/element/i_element.md b/Documentation/ProjectFile/gml/surfaces/surface/element/i_element.md
index 576add64edccf5d980a0ff86143dc43a7109a788..e9552bc218788ced6fad05d0761c712194b9bbc3 100644
--- a/Documentation/ProjectFile/gml/surfaces/surface/element/i_element.md
+++ b/Documentation/ProjectFile/gml/surfaces/surface/element/i_element.md
@@ -1 +1,3 @@
-\ogs_missing_documentation
+Defines a triangle by its three points.
+The face normal of the triangle is determined such that the points are
+located counter-clockwise around it (right-hand rule).
diff --git a/Documentation/ProjectFile/gml/surfaces/surface/i_surface.md b/Documentation/ProjectFile/gml/surfaces/surface/i_surface.md
index 576add64edccf5d980a0ff86143dc43a7109a788..642b503ea8724b3b36e9e43e3f073c14dff6896f 100644
--- a/Documentation/ProjectFile/gml/surfaces/surface/i_surface.md
+++ b/Documentation/ProjectFile/gml/surfaces/surface/i_surface.md
@@ -1 +1,2 @@
-\ogs_missing_documentation
+Defines a single triangulated surface.
+The surface is given as the set of all triangles it comprises.
diff --git a/Documentation/ProjectFile/gml/t_name.md b/Documentation/ProjectFile/gml/t_name.md
index 576add64edccf5d980a0ff86143dc43a7109a788..f081c356a48d8045a22c1977da78d7706b31a7b0 100644
--- a/Documentation/ProjectFile/gml/t_name.md
+++ b/Documentation/ProjectFile/gml/t_name.md
@@ -1 +1,4 @@
-\ogs_missing_documentation
+Name of the geometrical set, i.e., the entirety of all geometries defined in
+this file.
+Each individual geometry additionally has an own name, which has to be unique in
+the geometrical set.