Vientiane is actually a bit complicated: there are Vientiane Province, Vientiane Prefecture, and the city Vientiane, which is the capital of Laos. Until 1989 all was the Vientiane Province, but then the half with the capital was split off and is now called Vientiane Province. So this page means Vientiane Province, the northern part which is also called Viangchan.
Vientiane Province has several areas of tower karst. Notable caves are found in the limestone towers along Nam Sueng River south of Vang Vieng. Like all over Laos the karst areas and their caves are almost unexplored, so there may be important discoveries in the future.