At the time the Prophet (sallallahu `alayhi wa sallam) migrated to Yathrib, the city was divided into distinct sections inhabited by the Arabs and the Jews, with a separate district allocated to each clan. Each division consisted of the residential quarters and the soil used for agricultural purposes while in another part they used to have their strongholds or fortress-like structures. (Al-Yahud fi Balad il-‘Arab, p. 116). They had fifty-nine such strongholds in Madinah.(7) Dr. Israel Welphenson writes about these strongholds:
“The fortresses were of great importance in Yathrib for the people belonging to a clan took shelter in them during raids by the enemy. They afforded protection to the women and children who retreated to them in times of clashes and forays while the men went out to engage with the enemy. These strongholds were also utilized as warehouses for the storage of food-grains and fruits as the enemy could easily pilfer them if left in the open places. Goods and arms were also kept in such citadels and caravans carrying the merchandise used to stop near them for the markets were usually held along the doors of these fortifications. The same bulwarks also housed the synagogues and educational institutions known as Midras.(8) The costly and valuable goods which were stored in the fortresses show that the religious scriptures were also kept in them.” Jewish leaders and chieftains used to assemble in these fortresses for consultations or for taking decisions on important issues which were usually sealed by taking an oath on the scripture.” (Al-Yahud fi Balad il-‘Arab, pp. 116-117)
Defining the word Utum, as these fortresses were called, Dr. Welphenson writes: “The term connotes, in Hebrew, to shut out or to obstruct. When it is used in connection with a wall it denotes such windows as are shut down from outside can be opened from inside. The word is also reflective of a defensive wall or rampart and with that, it is safe to presume that Utum was the name given by the Jews to their fortresses. They had shutters which could be closed from the outer side and opened from the inner side.”
Yathrib was, thus, a cluster of such strongholds or fortified suburbs which had taken the shape of a town because of their proximity. The Qur’an also hints to this peculiar feature of the city in these words:
“That which Allah giveth as spoil unto His messenger from the people of the township.” [Qur’an 59:7]
Again, another reference of Madinah signifies the same peculiarity.
“They will not fight against you in a body save in fortified villages or from walls.” [Qur’an 59:14]
Lava plains occupy a place of special importance in the physical geography of Madeenah. These plains, formed by the matter flowing from a volcano which cools into rocks of burnt basalt of dark brown and black color and of irregular shape and size, stretch out far and wide and cannot be traversed either by foot or even on horses or camels. Two of these lava plains are more extensive; one is to the east and is known as Harrat Waqim, while the other lies in the west and is called Harrat Wabarah. Majduddin Firozabadi writes in the Al-Maghanim al-Matabata fi Ma’alim Ut-Tabbah that there are several lava plains surrounding Medina. The two lava plains of the east and west have virtually made the city a fortified refuge that can be attacked only from the north (where ditches were dug on the occasion of the battle of the trenches). On the southern side, the oases thickets and clumped date-palm groves as well as inter-tied houses of the densely populated area defend the city against incursion by an enemy.(9) The strategic location of Madinah was one of the factors responsible for its selection as the émigré’s new home.
Harrata Waqim, which is located east of the city and is arrayed with numerous verdant oases, was more populous than Harrata Wabarah. When the Prophet (sallallahu `alayhi wa sallam) emigrated to Yathrib, the more influential Jewish tribes, like, Banu an-Nadir and Banu Quraydha, were living in Harrata Waqim along with some of the important clans of Aus, such as, Banu ‘Abdul Ash’hal, Banu Haritha and Banu Mu’awiya. The eastern lava plain was thus named Waqim because of a locality which boasts of the same name in the district occupied by Bani ‘Abdul Ash’hal.(10)
 Al-Samhudi, Wafa-ul-wafa’ fi Akbar ul-Mustafa, Vol. P. 116.
 An abbreviation of Bet ha-Midras, signifying house of study or the place where students of the law gathered to listen to Midrash. Used in contradiction to the Bet ha-Sefer i.e. the primary school attended by children under the age of thirteen years to learn the scriptures, it goes without saying that the Jews of Medina had higher institutions of learning. (Jewish Encyclopedia, Vol. II, Art. Bet ha-Midras).
 Al-maghanim al-Matabata fi Ma’alim ut-Tabbah, pp. 108-114.
 Dr. Muhammad Husain Haikal, Mazal-al-Wahy, p. 557