Great place near Beyoğlu and Taksim. You will have access to both north and south side of İstiklal road. The historic Beyoğlu to Karaköy tunnel is about 10 minutes walk, after which you can take the ferry to either Eminönü (for the blue mosque and grand bazar area) or the Kadıköy port for the Asia side for just 5 TRY.
Great clean place with water boiler, mini kitchen, fridge and stove. In case you want to purchase some water, walk down two blocks and there's a general store nearby.
It's on a high floor but elevator access is available.