Galata Tower, Galata Kulesi
Located at top of the hill, you can enjoy the panoramic vista of Istanbul, from Bosphorus sea to the old city center to Golden Horn to Taksim area and more.
I can’t say it’s breathtaking, but it’d be worth 25TL ($8.50) entrance fee.
And on the way down, try the stairs instead of elevators which would be much more fun to take a look at some of the medieval inner structures and things (some new included).
Entrance Fee: 25TL ($8.50 USD)
Opening Hours 09:00~20:00