Kalen is a great host. It is a nice location near grand bazaar.
He is an avid reader and has a lot of information for great places in Istanbul. He suggested place for Turkish hamam which local prefers; it was amazing and refreshing, we had a great time.
Kalen can help you connect with right people or right places to enjoy your stay at Istanbul. During our one day stay with him we went for shopping, had a turkish bath and went to dinner cruise.
He is a great host who can help making your stay memorable. :)