The city desperately needed rain after a mild and dry winter, and it seems that we now have days (maybe weeks) of rain ahead.
I thought this thread might be a place to suggest things to do when it rains.
For me, Istanbul is a very outdoor city as I'm interested in walking and looking at views. However, here's my suggestions if what visitors can do on a rainy day:
1. Visit the aquarium. There are two: one in Florya (bigger and better), and another in Forum shopping centre.
2. Grand Bazaar tour, lunch inside and touring some of the old Hans.
3. Emirgan Park (yes, complete with rain but it will be empty), followed by breakfast/lunch at a restaurant on the Bosphorus, and then the Sabanci Museum.
4. Ferry ride. Quite romantic when it's raining.
5. Shopping centre, if that's your sort of thing.
Anyone have other suggestions?