JSFiddle - React, Tailwind, and code Playground

HTML

<nav>
    <ul>
        <li><a href="index.html">Home</a>
            <ul>
                <li><a href="#">teadsfasdfadsst</a></li>
            </ul>
        </li>

        <li><a href="#">Gallery</a></li>
        <li><a href="#">Map</a></li>
    </ul>
</nav>

CSS

nav {
    background-color: #004b98;
    width: 100%;
    margin: 0;
    padding: 0;
}

nav ul {
    margin: 0 auto;
    padding: 0;
    width: 900px;
    position: relative;
}

ul li {
    background-color: #004b98;
    float: left;
    list-style-type: none;
    border: 1px solid white;
    border-radius: 5px;
    margin: 5px;
    padding: 0;
}

nav ul li a {
    color: #ffffff;
    display: block;
    font-family: sans-serif;
    text-decoration: none;
    padding: 5px;
}

nav ul li:hover {
    background-color: #0069d4;
}

nav ul li {
    float: left;
    min-height: 1px;
    vertical-align: middle;
}

nav ul ul {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    width: 100%;
}

nav ul li:hover > ul {
    display: block;
}

nav ul li:hover {
    position: relative;
    cursor: default;
    color: black;
}
ul ul {bottom: 0; left: 0; margin-top: 0;}
nav:after {
    content:'';
    clear:both;
    display:table;
}