Imros Castle (Rumelifeneri Castle)
Imros castle  appears after a green corridor on the road from the edge of Sarıyer to the Black Sea. This is the place where the blue, calm river of the Sea of marmara is replaced by dark blue, raging waves. Imros consists of a vaulted entrance made of cut stone and a long arched wall that connects two towers.
Imros castle, which has now become a day trip attraction, was originally built by the Genoese to protect the entrance to the Bosporus from the western Black Sea. The Yoros Castle and Rumeli Kavağı can be seen on the opposite shore. The Imros Castle, built at the beginning of the 17th century by Murad IV. Rebuilt in the Ottoman period, was used as a military patrol point during the Republican period. According to historical sources, during this period there were 60 military dwellings, 100 cannons, an armoury, wheat depots and a mosque. This site is classified as a military base where 300 soldiers lived. Baedeker's Constantinople, 285