Positioning a div below its' parent. position: absolute; bottom: 0; not working?

Question

Basically I need to make a circle look like it's hanging from a string. I used the basic CSS of:

#string {
    position: relative;
}
#circle {
    position: absolute;
    bottom: 0;
}

And it's putting the circle at the bottom, but not below the "string" It's sitting on the right side of it, but at the bottom. Am I stupid? What am I doing wrong?

EDIT: Full code

<div class="anchor" id="one">
    <div class="circle" id="one">
    </div>
</div>

html, body { height: 100%; width: 100%; }
body {
    font: 100%/1.4 Verdana, Arial, Helvetica, sans-serif;
    background: #DDD;
    margin: 0;
    padding: 0;
    color: #000;
}
.anchor {
    background-color: #000;
        position: relative;
    width: 10px;
}
.anchor#one {
    margin-left: 10%;
    height: 500px;
}
.circle {
    position: absolute;
    bottom: 0;
    border-radius: 50%;
    background-color: #000;
}   
.circle#one {
    width: 200px;
    height: 200px;
}

Answer 1

bottom sets the distance of the element's bottom border to its offset parent.

To do what you want, you need to use top:

#circle {
    position: absolute;
    top: 100%;
}

Answer 2

<div class="anchor" >
    <div class="circle" >
    </div>
</div>

css

.anchor {
    background-color: #000;
    position: relative;
    width: 10px;
    margin-left: 10%;
    height: 500px;
}
.circle {
    position: absolute;
    bottom: -200px;
    border-radius: 50%;
    background-color: #000;
    width: 200px;
    height: 200px;
    left: -100px;
}