diff --git a/lidar_pipeline/ign.py b/lidar_pipeline/ign.py
index dd4b128..6d1d985 100644
--- a/lidar_pipeline/ign.py
+++ b/lidar_pipeline/ign.py
@@ -76,6 +76,8 @@ def _lat_lon_to_px(lat, lon, zoom, tile_size=256):
 def download_ign_tiles(min_x, max_x, min_y, max_y, layer, zoom_level=15):
     """Download IGN WMTS tiles for the given bounds using Web Mercator (PM).
 
+    If the first tile returns 404, automatically retries at lower zoom levels.
+
     Args:
         min_x, max_x, min_y, max_y: Bounds in Lambert 93.
         layer: IGN WMTS layer name.
@@ -106,76 +108,100 @@ def download_ign_tiles(min_x, max_x, min_y, max_y, layer, zoom_level=15):
     tile_matrix_set = "PM"
     tile_size = 256
 
-    col_min, row_min = _lat_lon_to_tile(nw_lat, nw_lon, zoom_level)
-    col_max, row_max = _lat_lon_to_tile(se_lat, se_lon, zoom_level)
+    # Try downloading at the requested zoom level; fall back to lower zooms on 404
+    min_zoom = 15
+    for zoom in range(zoom_level, min_zoom - 1, -1):
+        col_min, row_min = _lat_lon_to_tile(nw_lat, nw_lon, zoom)
+        col_max, row_max = _lat_lon_to_tile(se_lat, se_lon, zoom)
 
-    nw_px_x, nw_px_y = _lat_lon_to_px(nw_lat, nw_lon, zoom_level)
-    se_px_x, se_px_y = _lat_lon_to_px(se_lat, se_lon, zoom_level)
+        nw_px_x, nw_px_y = _lat_lon_to_px(nw_lat, nw_lon, zoom)
+        se_px_x, se_px_y = _lat_lon_to_px(se_lat, se_lon, zoom)
 
-    out_width = int(se_px_x - nw_px_x)
-    out_height = int(se_px_y - nw_px_y)
+        out_width = int(se_px_x - nw_px_x)
+        out_height = int(se_px_y - nw_px_y)
 
-    if out_width <= 0 or out_height <= 0 or out_width > 10000 or out_height > 10000:
-        logger.warning(f"    Image IGN trop grande: {out_width}x{out_height}px — abandon")
-        return None
+        if out_width <= 0 or out_height <= 0 or out_width > 10000 or out_height > 10000:
+            logger.warning(f"    Image IGN trop grande: {out_width}x{out_height}px — zoom {zoom} abandon")
+            continue
 
-    total_tiles = (col_max - col_min + 1) * (row_max - row_min + 1)
-    logger.info(f"    Zoom {zoom_level}: {total_tiles} tuiles à télécharger ({out_width}x{out_height}px)")
+        total_tiles = (col_max - col_min + 1) * (row_max - row_min + 1)
+        if zoom < zoom_level:
+            logger.info(f"    ↓ Retry zoom {zoom_level}→{zoom}: {total_tiles} tuiles ({out_width}x{out_height}px)")
+        else:
+            logger.info(f"    Zoom {zoom}: {total_tiles} tuiles à télécharger ({out_width}x{out_height}px)")
 
-    composite = np.full((out_height, out_width, 3), 255, dtype=np.uint8)
+        composite = np.full((out_height, out_width, 3), 255, dtype=np.uint8)
 
-    tiles_downloaded = 0
-    fmt = "image/png" if 'PLAN' in layer else "image/jpeg"
+        tiles_downloaded = 0
+        tiles_404 = 0
+        fmt = "image/png" if 'PLAN' in layer else "image/jpeg"
 
-    for col in range(col_min, col_max + 1):
-        for row in range(row_min, row_max + 1):
-            url = (
-                f"{wmts_url}?SERVICE=WMTS&VERSION=1.0.0&REQUEST=GetTile"
-                f"&LAYER={layer}&STYLE=normal"
-                f"&TILEMATRIXSET={tile_matrix_set}"
-                f"&TILEMATRIX={zoom_level}&TILECOL={col}&TILEROW={row}"
-                f"&FORMAT={fmt}"
-            )
+        for col in range(col_min, col_max + 1):
+            for row in range(row_min, row_max + 1):
+                url = (
+                    f"{wmts_url}?SERVICE=WMTS&VERSION=1.0.0&REQUEST=GetTile"
+                    f"&LAYER={layer}&STYLE=normal"
+                    f"&TILEMATRIXSET={tile_matrix_set}"
+                    f"&TILEMATRIX={zoom}&TILECOL={col}&TILEROW={row}"
+                    f"&FORMAT={fmt}"
+                )
 
-            try:
-                req = urllib.request.Request(url, headers={'User-Agent': 'Mozilla/5.0'})
-                with urllib.request.urlopen(req, timeout=10) as response:
-                    tile_data = response.read()
-                    tile_img = PILImage.open(io.BytesIO(tile_data)).convert('RGB')
-                    tile_arr = np.array(tile_img)
+                try:
+                    req = urllib.request.Request(url, headers={'User-Agent': 'Mozilla/5.0'})
+                    with urllib.request.urlopen(req, timeout=10) as response:
+                        tile_data = response.read()
+                        tile_img = PILImage.open(io.BytesIO(tile_data)).convert('RGB')
+                        tile_arr = np.array(tile_img)
 
-                    tile_origin_x = col * tile_size
-                    tile_origin_y = row * tile_size
+                        tile_origin_x = col * tile_size
+                        tile_origin_y = row * tile_size
 
-                    px_x = int(tile_origin_x - nw_px_x)
-                    px_y = int(tile_origin_y - nw_px_y)
+                        px_x = int(tile_origin_x - nw_px_x)
+                        px_y = int(tile_origin_y - nw_px_y)
 
-                    x_off = max(0, -px_x)
-                    y_off = max(0, -px_y)
-                    dst_x_start = max(0, px_x)
-                    dst_y_start = max(0, px_y)
-                    dst_x_end = min(out_width, px_x + tile_size)
-                    dst_y_end = min(out_height, px_y + tile_size)
+                        x_off = max(0, -px_x)
+                        y_off = max(0, -px_y)
+                        dst_x_start = max(0, px_x)
+                        dst_y_start = max(0, px_y)
+                        dst_x_end = min(out_width, px_x + tile_size)
+                        dst_y_end = min(out_height, px_y + tile_size)
 
-                    src_x = x_off
-                    src_y = y_off
-                    src_w = dst_x_end - dst_x_start
-                    src_h = dst_y_end - dst_y_start
+                        src_x = x_off
+                        src_y = y_off
+                        src_w = dst_x_end - dst_x_start
+                        src_h = dst_y_end - dst_y_start
 
-                    if src_w > 0 and src_h > 0 and tile_arr.shape[0] >= src_y + src_h and tile_arr.shape[1] >= src_x + src_w:
-                        composite[dst_y_start:dst_y_end, dst_x_start:dst_x_end] = \
-                            tile_arr[src_y:src_y+src_h, src_x:src_x+src_w]
-                        tiles_downloaded += 1
+                        if src_w > 0 and src_h > 0 and tile_arr.shape[0] >= src_y + src_h and tile_arr.shape[1] >= src_x + src_w:
+                            composite[dst_y_start:dst_y_end, dst_x_start:dst_x_end] = \
+                                tile_arr[src_y:src_y+src_h, src_x:src_x+src_w]
+                            tiles_downloaded += 1
 
-            except Exception as e:
-                if tiles_downloaded == 0 and col == col_min and row == row_min:
-                    logger.error(f"    ✗ Erreur tuile IGN: {e}")
+                except urllib.error.HTTPError as e:
+                    if e.code == 404:
+                        tiles_404 += 1
+                        # If the very first tile is 404, this zoom level is unavailable
+                        if col == col_min and row == row_min:
+                            logger.info(f"    Zoom {zoom} non disponible (404) — essai zoom inférieur")
+                            break
+                    continue
+                except Exception:
+                    continue
+            else:
                 continue
+            # Only reach here if inner loop broke (first tile 404)
+            break
 
-    logger.info(f"    → {tiles_downloaded} tuiles IGN téléchargées ({layer})")
-    if tiles_downloaded == 0:
-        return None
-    return composite
+        if tiles_404 > 0 and tiles_downloaded == 0:
+            # No tiles at this zoom, try lower
+            continue
+
+        logger.info(f"    → {tiles_downloaded} tuiles IGN téléchargées ({layer})")
+        if tiles_downloaded == 0:
+            continue
+        return composite
+
+    logger.error("    ✗ Aucun zoom disponible pour cette zone")
+    return None
 
 
 def generate_ign_overlay(dem_file, basename, vis_dir, resolution, layer, title, legend_label, description, out_suffix):