Above the city, on its isthmus, the citadel is an unavoidable walk. At the top of it, it offers an amazing view on the city. 
When you will see the size of the citadel stronghold, it will make you think of the decisive importance of the Island to control the entrance of the Black Sea.
The garrison was important and the amount of bulwarks, ditches, defense facilities will give you a strong impression.
During our trip, there were renovations (mainly thanks to European funds) even when it was the highest peak of heat at noon.
Having a fresh bottle of water during your visit is imperative. Climbing to the top of the citadel is quite substantial.