.chambres{
    border:10px solid #fff;
    display:block;
    margin:0 auto;
    box-shadow: 0 0 10px #000;
}
.block{
    margin-top: 20px;
    margin-bottom: 20px;
}

@media screen and (max-width: 660px) {
    .block{margin: 0;}
    .chambres{
    width: 100%;
    margin: 10px auto;
    box-sizing: border-box;
    }
}