Constantinople — also known as, amongst other things, Byzantium, New Rome, Kostantiniyye, Islambol, Stamboul, Astanih and (since c.1930 although also before) Istanbul
There is, as you might expect, some debate about the origin of the name Istanbul, but the dominant theory is that it’s a local corruption of the the Greek phrase eis tan polin “in the city” (Online Etymology Dictionary). Constantinople is, obviously, Constantine’s City.
Rumeli Hisarı was a 15th century fortress, built to the north of the city. Approximately here on Google Street View (the two main towers can be seen).
At the narrowest part of the Bosphorus, Sultan Mehmet the Conqueror ordered the great fortress of Rumeli Hisarı to be built on the European shore in order to control commercial and military traffic in preparation for the siege of Constantinople. He pitted his pashas (generals) against one another, daring them all to be the first to complete his particular tower and crenellated walls. The competition was fierce, and the huge fortress was completed in only four months.
Once completed, Rumeli Hisarı, along with Anadolu Hisarı on the Asian shore just opposite, controlled all traffic on the Bosphorus, and cut the city of Constantinople off from resupply by sea from the north. The mighty fortress’s useful military life was less than one year. Mehmet’s armines conquered the Byzantine capital several months later, and then there was no need for Rumeli Hisarı.
Turkey Travel Planner
The Rumeli Fortress (Rumelihisari) is located on the European (Rumeli) side of the Bosphorus. It was built by Mehmed II in four months beginning in the spring of 1452 across the waters from the Anatolian Fortress (Anadoluhisari or Güzelce Hisar) built by his grandfather Bayezid I (1389-1402). The aim was to establish control of the waterway at this narrowest point of the strait (660m) where ships would need to approach the shore to avoid the strong currents. A batallion of four hundred soldiers were stationed at the fortress (hisar) beginning in 1452, and prevented the passage of ships with canon fire during the siege of Constantinople. It is hence, also known as the Bogazkesen or the Controller of the Straits.
Archnet vis the WayBack Machine.