SOURCE

<div class="box">
    <div class="circle1"></div>
</div>

.box{
    width: 200px;
    height: 200px;
    margin: auto;
    border: 1px solid black;
    position: relative
}
.circle1{
    position: absolute;
    border: 1px solid black;
    width: 200px;
    height: 200px;
    border-radius: 50%;
    top:50%;
    left: 50%;
    transform: translate(-50%,-50%)
    
}
.circle1::before{
    content: '';
    position: absolute;
    border: 1px solid black;
    width: 100px;
    height: 100px;
    border-radius: 50%;
    top:50%;
    left: 50%;
    transform: translate(-50%,-50%)
}