404 when viewing assets I'm having some trouble getting started with Craft.

I'm attempting to upload some image assets for the first time. 

I've set up an asset source. I've tried using both a relative and an absolute path to the file. I am certain that the absolute path name is correct  because I simply copied from the pwd command on my server. Also, when I look in the directory, I see the uploaded images.

I've also supplied a url for the source. (I've actually tried a few different ones.)

Every time I've made a change, I've gone into settings and run Update Asset Indexes just to be sure everything was up to date.

However, when I try to view the images, I get a 404. I've tried typing the URL into the address bar, as well as clicking on "View asset" on the assets page. 

I did see this similar question, but I'm not running an nginx server. I'm running Apache.

I would love any insight on what I could be doing wrong. If you need any additional information, I'll be more than happy to edit it in.

Edit: For clarity, I'm trying to set up my file directory and my url to have different structures, which I believe is possible. For example, I want my images to be in public_html/media/images, but I want the url for images to be http://mysite.com/images. Doing that seems to be what causes the problem.
I'll use myself as an example, so if something isn't right we'll know who to blame.

First thing I do is set up an environment variable in my craft/config/general.php file like this:

...
'.dev' =&gt; array(
    'devMode' =&gt; true,
    'siteUrl' =&gt; 'http://mysite.dev/',
    'environmentVariables' =&gt; array(
        'basePath' =&gt; $_SERVER['DOCUMENT_ROOT'] . '/',
        'baseUrl' =&gt; 'http://mysite.dev/',
    )
)
...


Then, when I am creating assets sources, I'll create a general "Images" source:

Name: Images
Handle: images
File System Path: {basePath}media/images/
URL: /media/images/


Note that I am using my environment variable in the file system path.

{basePath}


You can call that whatever you want, it just has to match.

So if you were to view the source of my site, an image that was uploaded would have the path of:

http://www.mysite.com/media/images/my-image.jpg


Hope this helps!