Most visitors to Istanbul probably do not realize that there is a fortress there. Located on the western shore of the Bosphorus (just south of Fatih Sultan Mehmet Bridge) is a fortress that dates back to pre-Ottoman rule. Rumeli Hisarı (roo-mel-li hee-sah-ruh) was built in 1452 by Sultan Mehmet the Conqueror in preparation for his invasion of Byzantine Constantinople. The sultan built the fortress across the Bosphorus from the Anadolou Hisarı. Strategically, the two fortresses are located at the narrowest point of the Bosphorus which allowed the Ottomans to prevent aid and supplies from ever reaching Constantinople.
These days, the fort is a museum and a nice place for a stroll to catch magnificent views of the Bosphorus from the European side. There is a small entry free.
The fort is closed on Wednesdays. In my opinion, the best time to go is Saturday morning because there is a town, within easy walking distance, that holds its weekly market then. Plus, there are plenty of cafes to catch a bite or drink.
There are several ways you can get to Rumeli Hisarı but I took the No 559C bus from Taksim Square. It ends at the town above the fortress and its about a 10 minute downhill walk from there. You can catch the return bus to Taksim. Just ask the driver for information.
Not many tourists come to Rumeli Hisarı so you can catch a bit of local life that’s not been tainted by tourism. You’ll truly be off the beaten path!