Wander along the water's edge and breathe some fresh air at Golden Horn Park. It's always nice watching the boats coming and going.
You'll soon discover why this Istanbul City Center place for ships to anchor is popular with travelers. If you're searching for more to do and see here, Blue Mosque, Hagia Sophia, and Topkapi Palace are in the area too. They won't take you very long to get to from Golden Horn Park.