These photos use a novel approach of linking a text description to the actual caption of the photo. From the alt text, from the written caption, and from the long description that caption links to. This approach works in, say, journalism sites where photos are given captions, as was the convention in the print newspapers they often emulate. It solves the problem of cluttering up pages with D. links to descriptions. It introduces its own problem of cluttering pages with two visible descriptions and one invisible description all of the same thing.
All descriptions occupy their own separate files.
Other techniques we could have used, but did not, include setting up a neighbouring single-pixel GIF the same height as the image that is itself a link to the long description. This is an unsatisfactory solution for various reasons. If you have graphics loading turned on, you never see the link, and might notice it only if you catch the status line changing as you happen to move the mouse over it. This technique tends to render you more blind than you already are. Solely in text-only browsers does this approach provide accessibility and elegance.