We"re peering down the winding Ngo Dong River at a group of rowboats meandering through rice paddy fields. This is Ninh Bình province in Vietnam, about 60 miles south of Hanoi. On these two-hour tours by traditional Vietnamese rowboat, visitors wend their way between limestone karst peaks, through grottoes, and, if they"re lucky, by workers harvesting rice in the fields, their wide-brimmed hats shielding them from the sun. Perhaps the most spectacular time to take this river cruise is around harvest time in late May and early June when the paddy fields are awash in a golden glow with a backdrop of bright green hillsides. But don"t be surprised if the person rowing your boat moves the oars from hands to feet. It"s tradition here for rowers to give their arms a break and let their legs take over.