This large metropolitan city has a population of more than 15 million people. Similar to many other European countries/cities it is very hot humid in the months of July and August, but makes for great long evenings. The best time to travel would be September and October where the weather is not as hot, but very pleasant.
A must see attraction for many travelers is Tokapi Palace this is the home to many sultans and wives.
The palace has amazing views of the Sea of Marmara and great for taking photos.