Edit in JSFiddle

.map_container {
  position: relative;
  margin: 20px auto;
  width: 85%;
  padding-bottom: 60%;
  height: 0;
  overflow: hidden;
}

.map_container iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100% !important;
  height: 100% !important;
  border: none;
}