Passage: The province is in the valley of the Mae Nam Kong (Mekong River), which also forms the border with Laos. There are highlands to the south. The Laotian capital Vientiane is only 25 kilometres away from the provincial capital of Nong Khai. The Thai–Lao Friendship Bridge, which connects the two countries, was built jointly by the governments of Thailand, Laos, and Australia, and was opened in 1994.

Question: Where in Laos is considered the main capital?
Vientiane