The little town of Tha Kaek, right across the Mekong River from Nakhon Phanom in Thailand was once an important trading center back in the French Colonial days. Now it's little more than a sleepy backwater, but it still may be worth a visit.
During the French colonial period, Tha Kaek was an important city, both for trade along the Mekong as well as a defensive outpost on the front lines with the Siamese, who weren't too happy giving up 'their' territory. As a result of the strong French presence, there are a lot of French colonial style buildings around town from the late nineteenth and early twentieth centuries, so if you're interested in such things, a stroll around the old city area can be a pleasant way to pass some time.
But the history of Tha Kaek doesn't start with the French. The area around the modern city was once an important part of the Sikhotabong Empire, which held sway over much of modern-day Laos and northeast Thailand for nearly a thousand years up until the eleventh century. One of the few signs of this ancient past is the Phra That Sikhotabong pagoda, on the banks of the river a few kilometers south of Tha Kaek.
The area around Tha Kaek is rich in natural scenery too, especially caves, but I didn't get to investigate these as they are really only reasonable to visit in the dry season from October to May.
You won't find a big tourism infrastructure in Tha Kaek. There are only a few good hotels and restaurants, but there's enough to give you some choice. You can really only get to Tha Kaek by bus or private tour. There is no airport, although it doesn't take long to get here from the Nakhon Phanom airport with the new Friendship Bridge in place.