diff --git a/editor/src/objects.rs b/editor/src/objects.rs
index 969c7882e7..fb5e486cd6 100644
--- a/editor/src/objects.rs
+++ b/editor/src/objects.rs
@@ -101,7 +101,7 @@ impl ID {
             ID::ExtraShape(id) => Some(draw_map.get_es(id).center()),
             ID::Parcel(id) => map.maybe_get_p(id).map(|p| Pt2D::center(&p.points)),
             ID::BusStop(id) => map.maybe_get_bs(id).map(|bs| bs.sidewalk_pos.pt(map)),
-            ID::Area(id) => map.maybe_get_a(id).map(|a| Pt2D::center(&a.points)),
+            ID::Area(id) => map.maybe_get_a(id).map(|a| a.polygon.center()),
             ID::Trip(id) => sim.get_canonical_pt_per_trip(id, map),
         }
     }
diff --git a/editor/src/plugins/debug/debug_polygon.rs b/editor/src/plugins/debug/debug_polygon.rs
index 1936771c1a..e2d77cab87 100644
--- a/editor/src/plugins/debug/debug_polygon.rs
+++ b/editor/src/plugins/debug/debug_polygon.rs
@@ -80,7 +80,7 @@ impl DebugPolygon {
             }
             Some(ID::Area(id)) => {
                 if ctx.input.contextual_action(Key::X, "debug area geometry") {
-                    let pts = &ctx.primary.map.get_a(id).points;
+                    let pts = &ctx.primary.map.get_a(id).polygon.points();
                     let center = if pts[0] == *pts.last().unwrap() {
                         // TODO The center looks really wrong for Volunteer Park and others, but I
                         // think it's because they have many points along some edges.
diff --git a/editor/src/render/area.rs b/editor/src/render/area.rs
index 24cde97231..03693b3dc0 100644
--- a/editor/src/render/area.rs
+++ b/editor/src/render/area.rs
@@ -7,25 +7,16 @@ use map_model::{Area, AreaID, AreaType, Map};
 
 pub struct DrawArea {
     pub id: AreaID,
-    fill_polygon: Polygon,
 }
 
 impl DrawArea {
     pub fn new(area: &Area, cs: &ColorScheme) -> (DrawArea, Color, Polygon) {
-        let fill_polygon = area.get_polygon();
         let color = match area.area_type {
             AreaType::Park => cs.get_def("park area", Color::rgb(200, 250, 204)),
             AreaType::Water => cs.get_def("water area", Color::rgb(170, 211, 223)),
         };
 
-        (
-            DrawArea {
-                id: area.id,
-                fill_polygon: fill_polygon.clone(),
-            },
-            color,
-            fill_polygon,
-        )
+        (DrawArea { id: area.id }, color, area.polygon.clone())
     }
 }
 
@@ -34,17 +25,17 @@ impl Renderable for DrawArea {
         ID::Area(self.id)
     }
 
-    fn draw(&self, g: &mut GfxCtx, opts: RenderOptions, _ctx: &DrawCtx) {
+    fn draw(&self, g: &mut GfxCtx, opts: RenderOptions, ctx: &DrawCtx) {
         if let Some(color) = opts.color {
-            g.draw_polygon(color, &self.fill_polygon);
+            g.draw_polygon(color, &ctx.map.get_a(self.id).polygon);
         }
     }
 
-    fn get_bounds(&self, _: &Map) -> Bounds {
-        self.fill_polygon.get_bounds()
+    fn get_bounds(&self, map: &Map) -> Bounds {
+        map.get_a(self.id).polygon.get_bounds()
     }
 
-    fn contains_pt(&self, pt: Pt2D, _: &Map) -> bool {
-        self.fill_polygon.contains_pt(pt)
+    fn contains_pt(&self, pt: Pt2D, map: &Map) -> bool {
+        map.get_a(self.id).polygon.contains_pt(pt)
     }
 }
diff --git a/map_model/src/area.rs b/map_model/src/area.rs
index d4d0aa9db6..3819622714 100644
--- a/map_model/src/area.rs
+++ b/map_model/src/area.rs
@@ -1,6 +1,5 @@
-use crate::LANE_THICKNESS;
 use abstutil;
-use geom::{PolyLine, Polygon, Pt2D};
+use geom::Polygon;
 use serde_derive::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::fmt;
@@ -25,8 +24,7 @@ pub enum AreaType {
 pub struct Area {
     pub id: AreaID,
     pub area_type: AreaType,
-    // Might be a closed loop or not -- waterways can be linear.
-    pub points: Vec<Pt2D>,
+    pub polygon: Polygon,
     pub osm_tags: BTreeMap<String, String>,
     pub osm_id: i64,
 }
@@ -34,13 +32,5 @@ pub struct Area {
 impl Area {
     pub fn dump_debug(&self) {
         println!("{}", abstutil::to_json(self));
-        println!("{}", PolyLine::new(self.points.clone()));
-    }
-
-    pub fn get_polygon(&self) -> Polygon {
-        if self.points[0] == *self.points.last().unwrap() {
-            return Polygon::new(&self.points);
-        }
-        PolyLine::new(self.points.clone()).make_polygons(LANE_THICKNESS)
     }
 }
diff --git a/map_model/src/make/half_map.rs b/map_model/src/make/half_map.rs
index 7a3f2f38c8..e13926a8ae 100644
--- a/map_model/src/make/half_map.rs
+++ b/map_model/src/make/half_map.rs
@@ -181,10 +181,17 @@ pub fn make_half_map(
     );
 
     for (idx, a) in data.areas.iter().enumerate() {
+        let pts = gps_bounds.must_convert(&a.points);
+        if pts[0] != *pts.last().unwrap() {
+            panic!(
+                "Unclosed Area from OSM {} with tags {:?}",
+                a.osm_id, a.osm_tags
+            );
+        }
         half_map.areas.push(Area {
             id: AreaID(idx),
             area_type: a.area_type,
-            points: gps_bounds.must_convert(&a.points),
+            polygon: Polygon::new(&pts),
             osm_tags: a.osm_tags.clone(),
             osm_id: a.osm_id,
         });