If you're in the are and interested in history - visit this one!
It cost me 10€ entry, and then I headed inside. There's a lift, but if you want to truly see everything, you cannot avoid the stairs. Overall there are about 500 of them, but as I combined lift with stairs, I climbed about 250, I guess.
The view from the top is nice, but the one from the Panorama Tower in the city is way better.