 Complete the following phrase:  At the end of the 11th century, the growing settlement in the valley was walled, though settlement continued outside the wall. As the town spread up the west slopes surrounding the Birsig river, that section was walled also. At the beginning of the 13th century, all these sections were included within a single wall that embraced both the valley and hill settlements. In 1362, the city began building a new, wider city wall, which also enclosed the suburbs. It is possible that the destruction wrought by the 