Moniak
Shiroko pole, Bulgaria
Monyak (Bulgarian) is a 12th-century medieval fortress in the Rhodope Mountains of southern Bulgaria, mentioned in the chronicles of the Fourth Crusade as Chastel de Moniac in Old French. It had a strategic role in protecting the Zhelezna Vrata Pass.
Fort data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).