The sestiere of San Polo is lively and full of little shops, restaurants and bars, and of course, the colorful Rialto markets.  Trading began here in the 11th century, and ever since, the erberia and pescheria markets have flourished.  For just as long, the Rialto Bridge has attracted people; today it swarms with tourists, and the canal below is equally thick with river traffic.  Built in 1588, it marks the center of the city.  Also in San Polo is the great Frari church, and Tintoretto's remarkable cycle of paintings in the Scuola di San Rocco.  Santa Croce is mainly a humble area, with the vast car park, Piazzale Roma, as well as a stretch of palazzi along the Grand Canal.