Commissioned by Murad VI's mother, Kösem Valide Sultan, this massive han (caravanserai) was built in 1651 and originally housed up to 3000 travellers and their animals every night. It's now dreadfully dilapidated and has an ugly Shiite mosque in its main courtyard. Views from the han's roof are spectacular, encompassing the Golden Horn, Bosphorus, Old City and Galata.
Access to the roof is normally off limits, but if you head to the upstairs floor the caretaker may offer to take you up. He will expect a tip for his effort.