Karaköy has incredible 1920s-1930s Art Deco architecture from when it was the financial center. Walk Kemankeş Caddesi and Mumhane Caddesi - every building is worth photographing.

The old Minerva Han building and Ottoman Bank headquarters are architectural gems. The geometric facades and stepped parapets are textbook Art Deco. Much more interesting than another mosque visit if you appreciate urban design.