Maybe you've sat in a River Walk cafe looking out at people riding by in open, flat-bottom barges. Go ahead -- give in and join 'em. An amusing, informative tour, lasting from 35 to 40 minutes, will take you more than 2 miles down the most built-up sections of the Paseo del Río, with interesting sights pointed out along the way. You'll learn a lot about the river and find out what all those folks you watched were laughing about. There are four spots on the river where you can buy a ticket and board a boat.