If you're bored with downtown Udon and looking for some nearby diversion, Phufoilum makes for a nice outing. 60-ish km from Udon, up in the mountains, superb view of the entire province of Udon, dinosaur park for the kids, and picnic areas and flower displays. No entry fee and you can get decent (actually quite good) food at the restaurant there for regular prices (2 plates basil pork on rice, on plate fried rice, 1 coke, 1 bottle water for 130 baht....try that at a park in the US!).
Camping sites also available.
If you're a bike rider and don't want to ride the entire distance from Udon, you can park your truck in Nongsaeng and ride the 20km up to the top. The ride down is a blast!









