a#cerrar-modal{
position: absolute;
  top: 1em;
  right: 1em;
  z-index: 100;
  color: #fff;
  font-weight: bold;
  cursor: pointer;
  background: #333;
  font-family: arial;
  font-size: 15px;
  width: 25px;
  height: 25px;
  line-height: 25px;
  text-align: center;
  border-radius: 50%;
  transition: all .5s;
  text-decoration: none;
  
}

#myModal img{
  width: 100%;
  height: auto;
}