Though it's not yet near Indiana Jones levels, forest is slowly reclaiming this attractive ruin. The massive stupa collapsed, but the imposing walls of several buildings still stand. One kilometre northeast of the train station, Wat Kudi Dao is well beyond the stomping ground of most visitors, so you'll likely have this ruin to yourself, compounding the site's eerie ambience.
Knowledge is hazy about its history, but it was founded in the early period and expanded after that.