Nakhon Phanom (นครพนม) means 'City of Mountains', but the undulating sugarloaf peaks all lie across the river in Laos, so you'll be admiring rather than climbing them. The views are fantastic, though, especially during a hazy sunrise.
Nakhon Phanom's temples have a distinctive style. This was once an important town in the Lan Xang Empire and, after that, Thai kings sent their best artisans to create new buildings. Later a vivid French influence crossed the Mekong and jumped into the mix.