Beşiktaş is one of the older neighborhoods of Istanbul, though not many historic buildings have survived. It is located on the Bosphorus surrounded by Kabataş, Ortaköy, and Taksim districts. If you are looking for a local rather than touristic trip, Beşiktaş would be one of the places with easy access, along with Kadıköy.
It is said that the word 'Beşiktaş' is the result of the transformation of the word 'Beş Taş' which means 'five stones'. The most famous admiral of the Ottoman Empire, Barbaros Hayreddin Pasha, built five stone pillars as ship moorings, hence the name Beştaş. In time, the name Beştaş turned into Beşiktaş, which literally means 'cradle stone'.
Barbaros Hayrettin Pasha built a waterside residence for himself in Beşiktaş and stayed there during his visits to Istanbul. He also built a mosque, a madrasah, and a primary school in this area. When he died in 1546, he was buried in a mausoleum constructed by Mimar Sinan.
Beşiktaş Bazaar is the main attraction of Beşiktaş. You can find cheap clothes, fresh fish, and vegetables in this marketplace (open bazaar). Inexpensive fish restaurants and meatball eateries (köfteci in Turkish) are abundant, especially around the fish market area.
You can also taste local cuisine in the restaurants which offer home-cooked Turkish meals. These restaurants are very small but they are mostly clean and reliable. For example, Balkan Restaurant, also preferred by students, is a good one in this category. Towards the end of the bazaar street, there are nice pubs and bars you can enjoy.
Its football team, Beşiktaş Gymnastics Club (Beşiktaş Jimnastik Kulübü), is very important for this neighborhood. It is one of the oldest sports clubs of Turkey, founded in 1903. The football team wears black and white shirts and is nicknamed the Black Eagles, and Beşiktaş is full of black and white flags, Black Eagle logos, and statues. The club's 33,000-seat BJK İnönü Stadium is one of the most scenic stadiums in the world, being on the Bosphorus seafront, southwest of the center of Beşiktaş. Especially on match days, this area is very crowded.
You can do a Bosphorus cruise starting from Beşiktaş either by municipality boats or much more frequent private boats (known as 'motor' in Turkish). Most of the cruises last an hour or an hour and a half.
Besides this stadium, the Istanbul Maritime Museum (İstanbul Deniz Müzesi), Dolmabahçe Palace, and Sinan Pasha Mosque are among other places of interest in Beşiktaş.
Beşiktaş is one of the transportation hubs of Istanbul. We will not go as far as to say all roads lead to Beşiktaş (that distinction belongs to Taksim), but it is surely pretty central.
You can take ferries from main districts of Istanbul such as Kadıköy, Eminönü, and Üsküdar. For more information, see ferry hours for boats serving the Bosphorus.
You can take dolmuş from Gümüşsuyu and Taksim.
Or you can take any bus with 'Beşiktaş' on its sign panel from pretty much everywhere in Istanbul.