Constantinople is still the capital of a large Mediterranean empire in the modern day. Your pick, Byzantine/Roman, or Ottoman. How might its urban development proceed, compared to modern Istanbul's? Obviously, there will be many differences between a Byzantine and Ottoman version, hell, even just between Byzantine versions, depending on how 1204 went for the city, so just pick whichever version you like and run with it.
A few things to consider:
- The borders of the city itself may or may not grow as sprawling as modern Istanbul's.
- The city's population density might be very different, as well.
- Construction has to deal with the same archeological slow downs as modern Istanbul, no matter who is in charge (well, maybe a particularly Iconoclastic Communist government wouldn't care, but thats too horrifying to consider).
- The core of the old city is dominated by monuments of some sort, so long as it is an imperial capital, limiting development there.
- Modern Istanbul's connections (bridge and tunnel) across the strait are largely outside the old city.