There is a Russian name for Istanbul - Царьгра́д (Tsargrad). The relevancy of this traditional name in our time can be glimpsed from the media org tsargrad.tv , a Russian equivalent of fox news.
It's not just a Russian name, it's the Slavic name for Constantinople. It's used in all Slavic-speaking countries when teaching Byzantine history, of course, written with slight distortions depending on the Slavic language in question