I stayed in this hostel for 4 nights in the 25 beds dorm and I enjoyed it very much.
Of course this is not a place for people who seek luxury, it is basic and you receive what you pay for.
The location is very close to Ayasofia and the Blue Mosque, Actually it is just behind Ayasofia and I attached a picture for Ayasofia that was taken from the balcony of our dorm.
I made good friends while staying in this hostel thanks to the friendly atmosphere of the hostel.
There is only one issue, like i said i stayed at the 25 beds dorm, it is not a good room if you want to stay in the winter time, 1st: it is cold, 2nd: when it rains it is really loud. But for my experience, it was very good.

This place isnt for any type of princesses thats for sure. Its one of the cheapest on the street thats one of its good points. If your traveling as a couple and your on quite a budget then its pretty ideal if you book into one of the double rooms (not the one on the ground floor its ridiculously loud morning and night). The managment are really friendly and willing to help with anything. Its a little cramped, breakfast is nice and youll recieve it promptly. I stayed there for 4 nights and the only thing I couldnt work out was why there were 3 men sleeping in the reception area at night? All in all a nice cosy place to stay whilst your exploring Istanbul.

This was our last stop after traveling through Europe all summer, and basically the only reason we didn't switch hostels was because we were too weary from traveling. The place is disgusting. The bathrooms are unbearable. We walked into our bedroom to find a stray cat asleep. I also brought bedbugs back to the States with me. A miserable experience, hundreds of dollars spent destroying my furniture. The owner is an amazing guy, but it just isn't worth it. Do not stay here!!!!

Mavi Guesthouse is made by Ali, who welcomed us with tea and loads of amazingly useful information on Istanbul and the whole of Turkey. He put us in contact with all the right people to make make sure we had a fantastic seamless trip around the coast of Turkey. The gueshouse is clean and basic, exactly what we were looking for at a great price. Ali went out of his way to help us and show us a good time! We definitely recommend Mavi Guesthouse and Ali, who is guaranteed to make you giggle.