Overlay example for leaflet.js v1 by d3noob

index.html

<!DOCTYPE html>
<html>
<head>
    <title>Simple Leaflet Map</title>
    <meta charset="utf-8" />
    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.6.0/dist/leaflet.css"
          integrity="sha512-xwE/Az9zrjBIphAcBb3F6JVqxf46+CDLwfLMHloNu6KEQCAWi6HcDUbeOfBIptF7tcCzusKFjFw2yuvEpDL9wQ=="
          crossorigin=""/></head>
<body>
    <div id="map" style="width: 600px; height: 400px"></div>

    <script src="https://unpkg.com/leaflet@1.6.0/dist/leaflet.js"
            integrity="sha512-gZwIG9x3wUXg2hdXF6+rVkLF/0Vi9U8D2Ntg4Ga5I5BZpVkVxlJWbSQtXPSiUTtC0TjtGOmxa1AJPuV0CPthew=="
            crossorigin=""></script>
    <script>

        var coolPlaces = new L.LayerGroup();

        L.marker([-41.29042, 174.78219])
            .bindPopup('Te Papa').addTo(coolPlaces),
        L.marker([-41.29437, 174.78405])
            .bindPopup('Embassy Theatre').addTo(coolPlaces),
        L.marker([-41.2895, 174.77803])
            .bindPopup('Michael Fowler Centre').addTo(coolPlaces),
        L.marker([-41.28313, 174.77736])
            .bindPopup('Leuven Belgin Beer Cafe').addTo(coolPlaces),
        L.polyline([
            [-41.28313, 174.77736],
            [-41.2895, 174.77803],
            [-41.29042, 174.78219],
            [-41.29437, 174.78405]
            ]
            ).addTo(coolPlaces);

      var osmLink = '<a href="//openstreetmap.org">OpenStreetMap</a>',
          otmLink = '<a href="//opentopomap.org/">OpenTopoMap</a>';
        
      var osmUrl = '//{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',
          osmAttrib = '&copy; ' + osmLink + ' Contributors',
          otmUrl = '//{s}.tile.opentopomap.org/{z}/{x}/{y}.png',
          otmAttrib = '&copy; '+otmLink+' Contributors';
  
      var osmMap = L.tileLayer(osmUrl, {attribution: osmAttrib}),
          otmMap = L.tileLayer(otmUrl, {attribution: otmAttrib});

      var map = L.map('map', {
			    layers: [osmMap] }) // only add one!
          .setView([-41.2858, 174.78682], 14);

      var baseLayers = {
			    "OSM Mapnik": osmMap,
			    "Topogrophy": otmMap
		    };

      var overlays = {
	        "Interesting places": coolPlaces
      };

      L.control.layers(baseLayers,overlays).addTo(map);

    </script>
</body>
</html>