diff --git a/extensions/extension_types.yaml b/extensions/extension_types.yaml
index e03073c50..f310dbb20 100644
--- a/extensions/extension_types.yaml
+++ b/extensions/extension_types.yaml
@@ -8,3 +8,35 @@ types:
     structure:
       start: point
       end: point
+  - name: coordinate
+    structure:
+      x: fp64
+      y: fp64
+  - name: crs_point
+    structure:
+      x: fp64
+      y: fp64
+      crs: string
+  - name: linestring
+    structure:
+      T: List<coordinate>
+  - name: polygon
+    structure:
+      T: List<List<coordinate>>
+  - name: multipoint
+    structure:
+      T: List<coordinate>
+  - name: multilinestring
+    structure:
+      T: List<linestring>
+  - name: multipolygon
+    structure:
+      T: List<polygon>
+  - name: any_simple_geometry
+    parameters:
+      - name: T
+        type: union<crs_point, linestring, polygon, multipoint, multilinestring, multipolygon>
+  - name: geometry
+    parameters:
+      - name: T
+        type: List<any_simple_geometry>
diff --git a/extensions/functions_geometry.yaml b/extensions/functions_geometry.yaml
new file mode 100644
index 000000000..4ffa2c725
--- /dev/null
+++ b/extensions/functions_geometry.yaml
@@ -0,0 +1,29 @@
+%YAML 1.2
+---
+scalar_functions:
+  -
+    name: "point"
+    description: >
+      Return a 2D point with the given `x` and `y` coordinate values.
+    impls:
+      - args:
+          - name: x
+            value: fp64
+          - name: y
+            value: fp64
+        return: geometry
+  -
+    name: "makeline"
+    description: >
+      Return a linestring containing the points of the two input geometries.
+      Repeated points at the beginning of input geometries are collapsed to a single point.
+
+      A linestring can be closed or simple.  A closed linestring starts and ends on the same
+      point. A simple linestring does not cross or touch itself.
+    impls:
+      - args:
+          - name: x
+            value: geometry
+          - name: y
+            value: geometry
+        return: geometry