It's in an old secret building and offers you one of the best sightseeing places of Istanbul on a rooftop. On a cold weather, I am not sure if it is gonna be as nice as it is on a clear day. You should ask locals about how to get there as it is not easy to find. It is closer to Grand Bazaar so if you are around, do not skip it.
View Gallery
View Gallery
View Gallery
View Gallery
If you like to see the city from a hidden rooftop behind the locked doors, have a look at it.
I think you have to tip a few liras to the guy who holds the key to the hidden rooftop.