See Istanbul's most important sites in a single day on a small group tour Skip the line to enter Hagia Sophia and Topkapi Palace Visit the Blue Mosque to understand Islam and its architecture Stroll around the Grand Bazaar with the best hints from an insider Learn about the Ottoman and Byzantine history from an expert guide Visit the best of Istanbul with a well-planned itinerary Walk in the Sultanahmet district, the oldest part of Istanbul, which is filled with ancient and contemporary streets and neighborhoods