In the time of Fatih Sultan mehmet when the ottoman empire conquered a land, they converted only the biggest religious building into a mosque as a symbol of acceptance of people and religions living there. Normally in that era such buildings were destroyed instead both in the west and in middle east. Maybe even in other parts of the world? After declaring he will convert hagia sophia into mosque fatih also declared all byzantenes people will be accepted as ottoman people from that day on and gave many autonomous rights to the christian community of that time afterwards. In the ottoman empire there was only ottomanism too so this was actually a norm for them. Only padishah's family, one family had the right to rule the empire and the rest of the people in the empire were accepted and called as ottoman citizens regardles of their faith or ethnicity. Imagine having more than 60 ethnicities live together for 600 years in a popular conflict zone. Ottomans are a thing of past now but for me this shows that they did somethings really well really righteously because otherwise its impossible to last that long in that location, in that geography