护城河
5.To protect their outer walls, many castles were surrounded by a moat (a water-filled ditch). Some castles used rivers as part of their moat, but most moats were man-made.
8.The Forbidden City is surrounded by 10-metre high walls and a 52-metre wide moat.
10.The area by the city moat, the suburbs and the broad grassland of the newly built residential areas in Beijing are all suitable for flying kites.


