It will be easier to learn about Istanbul Regions by dividing Istanbul map into three zones. Each zone has a different color.
Yellow zone is historical peninsula, heart of Byzantium, and Ottoman Empire’s capital. Today, it is the most famous spot in Istanbul, where many historical monuments and other tourist attractions are packed inside. You will probably spend most of your time in historical peninsula during your visit, and the places you will see areTopkapi Palace, Hagia Sophia, Basilica Cistern, Blue Mosque, Spice Bazaar, New Valide Mosque, Grand Bazaar,Suleymaniye Mosque, Valens Aqueduct. All of the attractions are in walkable distance to each other, and you need to spend at least two days to visit major sights.
Purple zone is in Anatolian side of Istanbul. Uskudar and Kadikoy neighborhoods are located in here. Major attractions are Haydarpasa Train Station, Maiden’s Tower, Sakirin Mosque and Mihrimah Sultan Mosque…
Bosphorus is the strait joining the Black Sea to the Sea of Marmara, it also separates Anatolian and European sides of Istanbul. On the map you can see Bosphorus between pink-yellow zones and purple zone.
Golden Horn (Halic) is the stream that flows to Bosphorus, which divides European side of the city. It is located between yellow and pink zones on the map.