Enclose by the wide loop of the Grand Canal, San polo is Venice's smallest sestiere but it includes the most lively part of Venice: Rialto. According to the tradition Rialto, since remotest time, was one of the oldest centres of life in the Venetian islands, where the first inhabitants, having escaped from the mainland, availing themselves the firmer and higher soil - and therefore safe from floods - concentrate their trade. Rialto was the most important centre of the new group of islands, and Rivo Altus, the ancient name, was indeed the name of the whole town until after the year 1000, when it eventually took the name of Venice.