Yep, draw a box and give it a border radius that is half the width of the box:
#circle {
background: #f00;
width: 200px;
height: 200px;
border-radius: 50%;
}
Working demo:
#circle {_x000D_
background: #f00;_x000D_
width: 200px;_x000D_
height: 200px;_x000D_
border-radius: 50%;_x000D_
}
_x000D_
<div id="circle"></div>
_x000D_