The Rumeli Fortress is located on the Thracean side of the Bosphorus in Istanbul. Built by Fatih Sultan Mehmed the Conqueror in 1452, its purpose was to prevent northern aid from reaching the Byzantine Empire. The construction took four months and involved a team of 1000 masons and 2000 workers. The fortress boasts three towers, erected by Candarlı Halil Pasha, Saruca Pasha and Zaganos Pasha respectively, each named after their builder. The area covers an expanse of 30,000 m² and hosts five entrances.