Istanbul is very important place not only in Turkey but the world. Istanbul is some time the biggest and the most crowded city in Europe. Though the Islam is predominant here, it coexists in harmony with many other religions as well. For Roman Catholics there are several prominent churches here in various and other languages. And of course a visit here should certainly include a few non-religious sites, especially the Grand Bazaar or the spice market. And a boat ride on the Bosporus is the things that can be remembered for long more on this in detailed can be found on namasteturkey.