This citadel was built by Mehmet the Conqueror across from the Anatolia Fortress (Anadolu Hisari) in preparation for what was to be the seventh and final Ottoman siege of the fortified Byzantine city. Constructed in only 4 months, the fortress served to cut off Black Sea traffic in and out of the city, together with the Anadolu Hisari built by his great-grandfather across the Bosphorus on the Asian shores. The Ottoman army eventually penetrated the city by carrying the Turkish galleons over land by way of a sled and pulley system, and dropping them into the Golden Horn and behind the city's defenses.