The ancient city gates were not only the exits and entrances
of cities but the defense installations.In reality city gates were a
system of a series of defense buildings,including generally the gate
tower,enclosure,enclosure,embrasured tower and lock tower.Sited on the
city wall with a gate,the 1-3-storeyed gate tower is the last line of
the system,in front of it located a small castle calling enclosure, on
which is a 1-4-storeyed embrasured tower with tens shooting
windows.Sited on the enclosure two-storeyed lock tower likes a small
enbrasured tower and on its three sides were also opened shooting
windows.
