By the 12th century much of the woodland in this area had been cleared for fuel and building and over the next few centuries, peat was extracted in large quantities. The pits gradually began to fill with water, forming a wetland landscape rich in wildlife. The waterways were vital for communications and commerce. By the 16th century, Norwich was the second largest city in England after London. Goods from the city were exported world-wide through Great Yarmouth. The arrival of the railways brought competition for waterways transport but also brought visitors to the Broads.