Located to the east of Jinshanling,
the Simatai division of the Great Wall
is 3,000 metres long and has 35 battle
forts. The wall rises and falls with the
precipitous mountain ridge, while
the battle forts are located high up the hills.
Alarm was raised by means of smoke signals, at night by fire. Smoke was produced by burning a mixture of wolf dung, sulfur and saltpeter. Shots were fired at the same time. Thus an alarm could be relayed over 500km within just a few hours.
This is the end of Great Wall Virtual Tour, thank you.