diff --git a/crates/fj-viewer/src/graphics/renderer.rs b/crates/fj-viewer/src/graphics/renderer.rs
index 4bc216ab7..c273b4084 100644
--- a/crates/fj-viewer/src/graphics/renderer.rs
+++ b/crates/fj-viewer/src/graphics/renderer.rs
@@ -224,6 +224,10 @@ impl Renderer {
         ));
     }
 
+    pub fn clear_geometry(&mut self) {
+        self.geometries.clear();
+    }
+
     /// Resizes the render surface.
     ///
     /// # Arguments
diff --git a/crates/fj-viewer/src/viewer.rs b/crates/fj-viewer/src/viewer.rs
index b539da5d8..3d8116bac 100644
--- a/crates/fj-viewer/src/viewer.rs
+++ b/crates/fj-viewer/src/viewer.rs
@@ -130,6 +130,12 @@ impl WindowHandle {
             window_id: self.id,
         });
     }
+
+    /// # Clear the contents of the window
+    pub fn clear(&self) {
+        self.event_loop
+            .send_event(EventLoopEvent::Clear { window_id: self.id });
+    }
 }
 
 #[derive(Clone)]
@@ -288,6 +294,22 @@ impl ApplicationHandler<EventLoopEvent> for Viewer {
 
                 window.add_displayable(displayable);
             }
+            EventLoopEvent::Clear { window_id } => {
+                let Some(winit_window_id) = self.id_map.get(&window_id) else {
+                    unreachable!(
+                        "Mappings for all window IDs are created when handling \
+                        the `Window` event."
+                    );
+                };
+                let Some(window) = self.windows.get_mut(winit_window_id) else {
+                    unreachable!(
+                        "We never remove any windows, so it's not possible to \
+                        have a mapping to an ID, but not a window with that ID."
+                    );
+                };
+
+                window.clear();
+            }
         }
     }
 }
@@ -300,4 +322,7 @@ enum EventLoopEvent {
         displayable: Displayable,
         window_id: u64,
     },
+    Clear {
+        window_id: u64,
+    },
 }
diff --git a/crates/fj-viewer/src/window.rs b/crates/fj-viewer/src/window.rs
index 7a946fcb2..a54f2e5b3 100644
--- a/crates/fj-viewer/src/window.rs
+++ b/crates/fj-viewer/src/window.rs
@@ -194,6 +194,11 @@ impl Window {
         self.should_render = true;
     }
 
+    /// # Clear the geometry displayed in the window
+    pub fn clear(&mut self) {
+        self.renderer.clear_geometry();
+    }
+
     /// # Draw the window
     pub fn draw(&mut self) -> bool {
         let size_is_invalid = {
diff --git a/experiments/2025-03-18/src/debug.rs b/experiments/2025-03-18/src/debug.rs
index b164d0a44..deb8273cc 100644
--- a/experiments/2025-03-18/src/debug.rs
+++ b/experiments/2025-03-18/src/debug.rs
@@ -56,6 +56,17 @@ impl DebugWindow {
 
         window.display_point(point);
     }
+
+    #[allow(unused)] // occasionally useful for debugging
+    pub fn clear(&self) {
+        let inner = self.inner.lock().unwrap();
+
+        let DebugWindowInner::Initialized { window } = inner.deref() else {
+            panic!("Debug window has not been initialized.");
+        };
+
+        window.clear();
+    }
 }
 
 enum DebugWindowInner {