JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
    
    <head>
        <title>CircleMarker tooltip</title>
        <meta charset="utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <link rel="stylesheet" href="http://leafletjs.com/dist/leaflet.css" />
        <!--[if lte IE 8]>
            <link rel="stylesheet" href="http://leafletjs.com/dist/leaflet.ie.css"
            />
        <![endif]-->
    </head>
    
    <body>
        <div id="map" style="width: 600px; height: 400px"></div>
        <script src="http://leafletjs.com/dist/leaflet.js"></script>
    </body>

</html>

JavaScript

var map = L.map('map').setView([51.9, 7.6], 11);

 L.tileLayer('http://{s}.tile.cloudmade.com/5e4495ff4b0d454eb0443225198b7e6c/997/256/{z}/{x}/{y}.png', {
     attribution:
         'Map data &copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, <a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, Imagery © <a href="http://cloudmade.com">CloudMade</a>',
     maxZoom: 16
 }).addTo(map);

 var polygon =
                        {"type": "Feature",
                         "properties": {
                            "name":"City BoundingBox",
                            "style": {
                                "color": "#004070",
                                "weight": 4,
                                "opacity": 1
                            } },
                            "geometry": {
                                "type": "Polygon",
                                "coordinates": [[
                                    [7.5,52.05],                
                                    [7.7,51.92],
                                    [7.6,51.84],
                                    [7.4,51.94],
                                    [7.5,52.05]
                                    ]]
                              }
                            };

var myLayer = L.geoJson(undefined, {
     style: function (feature) {
         return feature.properties.style;
     },
     onEachFeature: function (feature, layer) {
         layer.bindPopup(feature.properties.name);
     }
 })

 myLayer.addData(polygon);
myLayer.addTo(map);