The first throw must be made from behind the wooden board which encloses the par course area, as noted above. The rock is not visible from the start, but can be seen clearly from the top of the hill (where the arrow above indicates). Note that the large tree to the right has drawn in at least one frisbee during every Septathalon.
This is the view from the spot indicated in the first photo.
The entire rock is the target, although the cement that it is placed upon does not count.
Course Update: The balance beam previously used as the starting line has been removed, so use an imaginary line next to the large rock by the bathroom. The "stinky tree" (in the distance behind the Animal in the first photo) is now usually trimmed back, making the approach slightly easier.