I cant remember what they were called, but I can tell you that they originated in Africa. Use that to research I have no doubt you will find it ;)
Claiming it as a historic item (which it is) through a document prevents common people to be affiliated with harming it. So by saying it is of significant history, citizens and tourists will not be able to do anything to jeopardize the natural landmark
Answer: I Think It's To Protect The Coast By Blocking Winds
Explanation: Hope It Help
The length of Shanghai is 676 kilometers or 420 mliles
