I visited this WHS in December 2013 before Christmas and in January 2014. The highlights of this WHS were the landmarks and unmissable Blue Mosque, Hagia Sophia and Topkapi Palace. Their interior and exterior beauty is sublime. Other noteworthy sites are the Basilica Cisterns, Chora Church (Byzantine jewel!), Galata Tower, Byzantine City Walls, the Grand Bazaar and the Spice Bazaar. The Sultanahmet area alone is definitely worth a visit even though there are plenty of other sites to visit.