Acording to the press release, between Vientiane and Vang Vien.
For those of you familiar with the road it's on the Nam Lik downstream of Hinheup which I believe is that major bridge on the way to Vang Vien.
If this link wears out as links are apt to do on Lao web sites try Green Discovery, they are the ones who installed it.
They need to think of a catchy name, good luck on nam lik, or Experience without Gibbons or something.
$50 but they say it's negotiable.