I don't know how these sometimes get past me, but they do...sorry about that.
Though there is detail in this shot, and it can be enhanced, There isn't an awful lot. The less there is, the tougher it is to enhance -- and that is probably why you are having trouble.
This is probably a case where 2 exposures would have been optimal. First, you would expose for the highlights, as apparently you have, and then you would expose for the shadows. With the two images, you can then merge the better content from each.
What you will have to try to do with this image is enhance what you have, but my guess is it will be easier and the results better to rebuild. Enhancements you make to the shadows will affect other parts of the image.
I made a quick attempt to enhance those shadows as they exist, and couldn't get very far without the image starting to posterize. Another direction which seemed to hold some promise was cropping. Cropping out much of the shadow would leave a lot less detail to attempt repair on. http://hiddenelements.com/files/attachment-3.jpg http://hiddenelements.com/files/attachment4.jpg
Anyone else giving this a try? other suggestions?