diff --git a/web/app.py b/web/app.py
index 4d4fc9e..495862a 100644
--- a/web/app.py
+++ b/web/app.py
@@ -134,7 +134,11 @@ async def security_headers(request: Request, call_next):
         "default-src 'self'; "
         "script-src 'self' https://cdn.tailwindcss.com https://unpkg.com; "
         "style-src 'self' https://cdn.tailwindcss.com https://unpkg.com 'unsafe-inline'; "
-        "img-src 'self' data: https://*.tile.openstreetmap.org https://tile.openstreetmap.org https://unpkg.com; "
+        "img-src 'self' data: "
+        "https://*.tile.openstreetmap.org https://tile.openstreetmap.org "
+        "https://*.basemaps.cartocdn.com https://basemaps.cartocdn.com "
+        "https://*.tiles.openrailwaymap.org https://tiles.openrailwaymap.org "
+        "https://unpkg.com; "
         "connect-src 'self'; frame-ancestors 'none';"
     )
     return resp
diff --git a/web/static/map.js b/web/static/map.js
index 9f6ec13..4f7e85d 100644
--- a/web/static/map.js
+++ b/web/static/map.js
@@ -48,7 +48,6 @@ function renderMarkers(data) {
     markerLayer = L.layerGroup().addTo(mapInstance);
   }
 
-  const bounds = [];
   data.forEach((f) => {
     if (typeof f.lat !== "number" || typeof f.lng !== "number") return;
     const rent = f.rent ? Math.round(f.rent) + " €" : "";
@@ -61,14 +60,7 @@ function renderMarkers(data) {
       `<b>${safeAddr}</b>` + (meta ? `<br>${meta}` : "") +
       `<br><a href="${safeLink}" target="_blank" rel="noopener">Zur Anzeige →</a>`,
     );
-    bounds.push([f.lat, f.lng]);
   });
-
-  if (bounds.length === 1) {
-    mapInstance.setView(bounds[0], 14);
-  } else if (bounds.length > 1) {
-    mapInstance.fitBounds(bounds, { padding: [30, 30] });
-  }
 }
 
 function buildMap(el) {
@@ -81,10 +73,18 @@ function buildMap(el) {
     touchZoom: false,
     keyboard: false,
   }).setView(BERLIN_CENTER, BERLIN_ZOOM);
-  L.tileLayer("https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png", {
-    attribution: "© OpenStreetMap",
-    maxZoom: 18,
+  // CartoDB Voyager — clean, Google-Maps-ish base style.
+  L.tileLayer("https://{s}.basemaps.cartocdn.com/rastertiles/voyager/{z}/{x}/{y}{r}.png", {
+    attribution: "© OpenStreetMap · © CARTO",
+    subdomains: "abcd",
+    maxZoom: 19,
+  }).addTo(mapInstance);
+  // Transit overlay — OpenRailwayMap highlights S-/U-/Tram-Linien.
+  L.tileLayer("https://{s}.tiles.openrailwaymap.org/standard/{z}/{x}/{y}.png", {
+    attribution: "© OpenRailwayMap",
     subdomains: "abc",
+    maxZoom: 19,
+    opacity: 0.75,
   }).addTo(mapInstance);
   markerLayer = L.layerGroup().addTo(mapInstance);
 }