ముహమ్మద్ ప్రవక్త మరణం తరువాత, వరదలు [[మక్కా]] నగరానికి తాకాయి, ఉమర్ ఆదేశాన [[కాబా]] ను రక్షించుటకు, రెండు డ్యామ్లు నిర్మించారు. [[మదీనా]] వద్ద కూడా ఒక డ్యామ్ ను వరదలనుండి రక్షణ కొరకు నిర్మించారు.<ref>Nadvi (2000), pg. 408</ref>
The area of [[Basra]] was very sparsely populated when it was conquered by the Muslims. During the reign of Umar, the Muslim army found it a suitable place to construct a base. Later the area was settled and a mosque was erected.
Upon the conquest of [[Madyan]], it was settled by Muslims. However, soon the environment was considered harsh and [[Umar]] ordered the resettlement of the 40,000 settlers to [[Kufa]]. The new buildings were constructed from mud bricks, instead of reeds, a material that was popular in the region, but caught fire easily.
During the conquest of Egypt the area of [[Fustat]] was used by the Muslim army as a base. Upon the conquest of Alexandria, the Muslims returned and settled in the same area. Initially the land was primarily used for pasture, but later buildings were constructed.<ref>Nadvi (2000), pg. 416-7</ref>
Other already populated areas were greatly expanded. At [[Mosul]], Harthama Arfaja, at the command of Umar, constructed a fort, few churches, a mosque and a locality for the Jewish population.<ref>Nadvi (2000), pg. 418</ref>