Kamianets-Podilskyi Fortress
The fortress above the Smotrych canyon — Podillia's main stronghold.
The town stands on a rock island cut by the river in a full ring, and the fortress locks the only natural entrance. The castle was expanded by the Lithuanian Koriatovych princes, and its might came with the Polish age: for centuries this was the Commonwealth's main outpost against the Ottomans. The Old Town with its Armenian, Polish and Ruthenian quarters is a day of its own, not an appendix to the fortress.
Honestly, fortress and Old Town are two different days. The canyon bridges catch the wind.