The following are the most important gates in history:

1. The Gates of Alexander: The Gates of Alexander were a barrier built by Alexander the Great in the Caucasus to keep the barbarians of the north from the south.
2. Sungnyemun Gate: Seoul, Korea
3. Kashmiri Gate: Delhi, India
4. Panama Canal Locks:the largest canal gates in the planet
5. Gates of Old City, Jerusalem: There were four gates to the Old City during the crusader Kingdom of Jerusalem. one set of gates on each side. Suleiman the top of the Ottoman empire built eleven gates. The gates closed before sunset and opened at sunrise. The gates are Gates Al Gadid, Gates Alamoud, Gates AlSahairad, Gates Sittna Maryam, Gates alMaghariba, Gates ElNabi Daoud, Gates alKhalel and 4 other sealed gates
6. Cairo Gates:

Gawhar El Sakaly during the Fatimid reign (969-1171) established El Fostat city or Cairo of El Moez which is now a part of greater Cairo. The city had many buildings and parks. It was a hub for rulers and princes. He installed walls including entry gates around the city to enter or exit the city.

The walls were instrumental to protect the city in case of war and for management of traffic in state of peace. The city was like a citadel. Some of Cairo Gates still exist till today.

The gates of Cairo are as follow:
Gates Al Wazer, It was built in 1174 by Qaraqush, Saladin’s Minister, to defend the capital. It is no longer exist. It was called Bab El Haded Gates

Gates El Bahr, one of the outside Cairo gates at the north wall

Gates El Seada

Gates El Selsela, El Jabel Citadel
It is known nowadays as Alarab Gates. It overlooked El Jabel Citadel. This gates was removed due to a crack in 1884.

Gates El GharebIt was destroyed and replaced by Al Azhar University.

Gates El Barkia, Built by Saladin in 1184

Gates El Gaded , built in 1170, It is still exist.

Gates El Husenia, This gate was destroyed in 1895.

Gates El Khalk , built in 1241

Gates El Khoga , No longer exist

Gates Darb El Laban, built in 1092, called Bab El Metwali.

Gates Qasr El Selehdar, established in 1347

Gates El Qela

Gates Al Akhdar, Was built by the Fatimid and still exist

Gates El Qantara, established by Salah El Din El Ayoubi in 1173, it is no longer exist

Gates El Ghory

Gates El Fetouh, established in 1087, it is still exist.

Gates El Nasr, established in 1085, it is still exist.

Gates Khan El Khalili, established in 1511, It is still exist

Gates El Tawfik, established in 1097

Gates El Farag

Gates Qayet Bey, established in 1494, other name is El Sayeda Aisha Gates