diff --git a/packages/display/src/Grid.ts b/packages/display/src/Grid.ts
index 4732672b..ab578468 100644
--- a/packages/display/src/Grid.ts
+++ b/packages/display/src/Grid.ts
@@ -43,6 +43,7 @@ export class GridTile implements ViewportTile {
     gridY: number;
 
     private bounds: number[][];
+    private resultCache: {};
 
     constructor(tileZoomLevel: number, x: number, y: number, size: number, gridX: number, gridY: number, bounds: number[][]) {
         this.quadkey = tileUtils.tileXYToQuadKey(tileZoomLevel, gridY, gridX);
@@ -54,6 +55,8 @@ export class GridTile implements ViewportTile {
         this.gridX = gridX;
         this.gridY = gridY;
         this.bounds = bounds;
+
+        this.resultCache = {};
     }
 
     static updateTileBBox(tx1: number, ty1: number, tileSize: number) {
@@ -88,6 +91,13 @@ export class GridTile implements ViewportTile {
         optimiseTileLevel: boolean = true,
         tiles: ViewportTile[] = []
     ): ViewportTile[] {
+        const cacheKey = minTileSize<<1|Number(optimiseTileLevel);
+        const cache = this.resultCache;
+        if (cache[cacheKey]) {
+            return cache[cacheKey];
+        }
+        cache[cacheKey] = tiles;
+
         let {tileZoomLevel, gridX, gridY, scaledSize: size} = this;
         if (size > minTileSize) {
             const displayScale = display.s;
diff --git a/packages/display/src/displays/BasicDisplay.ts b/packages/display/src/displays/BasicDisplay.ts
index 6d082aab..31cfefb5 100644
--- a/packages/display/src/displays/BasicDisplay.ts
+++ b/packages/display/src/displays/BasicDisplay.ts
@@ -412,7 +412,9 @@ abstract class Display {
                         displayTile.i = ++this.ti;
                         screenTiles.push(gridTile);
 
-                        if (!vpTiles.find((t) => t.quadkey == quadkey && t.x == gridTile.x && t.y == gridTile.y)) {
+                        if (!vpTiles.find((t) => t.quadkey == quadkey
+                            // At the most zoomed-out level, tiles may repeat multiple times to fully cover the screen.
+                            && t.x == gridTile.x && t.y == gridTile.y)) {
                             vpTiles.push(gridTile);
                         }
                         display.initTile(displayTile, dLayer);