Sepon is a river and a border crossing point between Laos and Vietnam in the southeast of Laos. It lies in the rural Savannakhet Province and while there's not much to see here, it's a nice destination to get way from it all for a few days.
The Sepon River is actually fairly shallow in most places - barely a few feet deep - while it stretches to over 100 yards in width. The water is clean and fresh and surrounded by jungle with tall trees and is perfect during the November through March dry season.
A fair amount of trade takes place between the Lao town of Lao Bao and Vietnam, where you can also make a border crossing in something like 30 minutes. Although there is not that much to see, there is a substantial gold mine here along with plenty of other attractions and national parks along the main highway 9.
Local buses are the best option for getting to Sepon, although the trip is fairly tough-going from Pakse via Seno and Muang Phin. The nearest international airport is in Pakse, but expect a full day's bus journey from there to Sepon.