For those of you who are interested in museums, here is a list of them located in Istanbul
If you are a frequent visitor of such places, remember to get a museum card;)
Have fun
İstanbul Toy Museum
http://www.istanbuloyuncakmuzesi.com/index.asp?lang=en
Rahmi M. Koç Museum
http://www.rmk-museum.org.tr/en/index.htm
İstanbul Archaeological Museum
http://icvb.org.tr/
Arter
http://www.arter.org.tr/W3/
İstanbul Modern
http://www.istanbulmodern.org/en
the Chora Church Museum
http://kariye.muze.gov.tr/en
Sadberk Hanım Museum
http://www.sadberkhanimmuzesi.org.tr/en/
Sakıp Sabancı Museum
http://www.sakipsabancimuzesi.org/en
Pelit Chocolate Museum
http://www.pelitcikolatamuzesi.com/en/
Pera Museum
https://www.peramuseum.org/
Panorama 1453
http://panoramikmuze.com/homepage/
Museum of Innocence
http://en.masumiyetmuzesi.org/
Museum card if you're interested in like half of the museums in the link below.
http://www.muzekart.com/en/museum-pass/about_27.html
Edit: Macka Modern Art Gallery
http://en.mackamodern.com/