let's start with the walls and gates of Damascus

The Old City of Damascus with an approximate area of 128 hectaresis surrounded by ramparts on the northern and eastern sides and part of the southern side. There are seven extant city gates, the oldest of which dates back to the Roman period. These are, clockwise from the north of the citadel:

1. Bab al-Faradis ("the gate of the orchards", or "of the paradise")
2. Bab al-Salam ("the gate of peace"), all on the north boundary of the Old City
3. Bab Tuma ("Touma" or "Thomas's Gate") in the north-east corner, leading into the Christian quarter of the same name,
4. Bab Sharqi ("eastern gate") in the east wall, the only one to retain its Roman plan
5. Bab Kisan in the south-east, from which tradition holds that Saint Paul made his escape from Damascus, lowered from the ramparts in a basket; this gate has been closed and turned into Chapel of Saint Paul marking this event,
6. Bab al-Saghir (The Small Gate)
7. Bab al-Jabiya at the entrance to Souk Midhat Pasha, in the south-west.   

There is also Bab al-Faraj which is located in the northern walls near the northeast corner of the citadel (the Citadel of Damascus), was built by Nur ad-Din Zangi in 1154–55.         source:Wikipedia.

plan of the ancient city of Damascus with the main gates marked on it.

According to Wikipedia Bab Sharqi, also known as the Gate of the Sun, is one of the eight ancient city gates of Damascus, Syria, and the only original Roman gate still standing. Its modern name comes from its location in the eastern side of the city.

 Bab Sharqi 

photo taken by me on 10th of March 2016.

this gate was built during Septimius Severus or Caracalla's era.

 i found this plan of the ancient city during the greek and the roman period, here it explains the meanings of each gate and how they used to connect these gateways with Gods from ancient religions. i added translation to the gates i am discussing in this part.

Bab Kisan, exterior and interior.    source: architecture of the islamic world

Bab Kisan is located in the southeastern part of the Old City,it was named in memory of a slave who became famous during a conquest by the Caliph Mu'awiya. The wall was built during the Roman era and was dedicated to Saturn. Bab Kisan was the escape route of St Paul.

Paul settled in Damascus after having claimed to have witnessed a vision where Jesus was on a road to the city. After staying three years in Damascus, he went to live in the Nabataean kingdom (which he called "Arabia") for an unknown period, then came back to Damascus, which by this time was under Nabatean rule. After three more years , he was forced to flee the city under the cover of night ,after explosive reactions from Jews who opposed his teachings. He was lowered down from a window in the wall, down into a basket, and with the help of hisChristian disciples, made his escape at night and fled towards Jerusalem. Paul recounts in the Bible that it was through a window that he escaped from a certain death . Today it holds the Chapel of Saint Paul.

source:wikipedia