Is the Asian side of the Bosphorus in Istanbul too far from Old Istanbul and Beyoğlu, on the European shore, to use as a base for your visit?
Not really.
If you're staying in Istanbul for just one or perhaps two nights, it makes perfect sense to stay in Old Istanbul because the top sights are there and you'll spend less time in transport.
But if you intend to visit any sights outside that area—Beyoğlu, the Golden Horn, the Bosphorus, the City Walls, the Princes Islands, etc.— the advantage diminishes.
Here's why: to go to any of these districts outside of Old Istanbul, you'll use public transit—just as you will if you start from the Asian shore. For example, you can start some Bosphorus cruises from either shore, so there's no huge advantage to being in Europe rather than Asia. And in any case, the duration of the pleasant ferry voyage between Kadıköy and the European-side districts of Eminönü and Karaköy is only 20 to 25 minutes, the cost only a few liras.
You can't get this view of Hagia Sophia in Old Istanbul—you have to be on the other shore of the Bosphorus.
Asian-Side Advantages
1. Lower prices: the hotels here are not (yet) as popular with tourist hordes.
2. Quiet neighborhoods: more of the Asian side is residential, so you may have quieter nights.
3. Views: when you're in Old Istanbul, you don't see Old Istanbul. For the best postcard views, gaze from Asia!
4. Bosphorus cruises: whenever you go to the European shore, you enjoy a fine 20-minute Bosphorus mini-cruise.
Good Hotels
With these thoughts in mind, have a look at the tidy, quiet, 16-room My Home Garden in Kadıköy, designed by a businessman—architect husband-and-wife team. On a quiet street less than a 10-minute walk from the dock for TurYol ferries to Eminönü and Karaköy on the European shore, it's also near Kadıköy's lively market district (çarşı) with its many fish restaurants and lively tavernas. All the comforts: Swiss-clean rooms, private bath with good shower, individual climate control, minibar fridge, in-room safe, an elevator/lift, a small but welcome private garden in the rear, and experienced, professional staff. More...
The neighborhoods within 10 minutes' walk of the Kadıköy ferry docks boast more than two dozen hotels, from modest hostels to the 5-star, 248-room Doubletree by Hilton Istanbul - Moda, which enjoys spectacular views of Old Istanbul and the Sea of Marmara. More...
Use this Hotel Search Box to find other good hotels and apartments/flats in Kadıköy on the Asian side:
—by Tom Brosnahan