.map-responsive {
    overflow: hidden;
    /* sets the aspect ratio (e.g., 56.25% for 16:9) */
    padding-bottom: 56.25%; 
    position: relative;
    height: 0;
}

.map-responsive iframe {
    left: 0;
    top: 0;
    height: 100%;
    width: 100%;
    position: absolute;
}