This must be one of the longest horns I have seen on a Rhino - even more spectacular is that it is a cow with a very young calf. The length of the calf's head and neck is only 2/3 of the mother's horn!
It was taken in the Hluhluwe Game Reserve in KwazuluNatal, South Africa in rainy weather. She was too far away for any flash to be effective.
Canon 40D
Exp. Time: 1/250sec
f/ 5.6
Focal length: 420mm
ISO 400.
That horn is something you do not see too often, altough I have seem someting similar in Khama Rhino Sanctuary in Botswana, strangely enough that was also a female. Unfortunately the grass was a little too long to get any good images.