I would suggest spending Sunday near bosphorus cost which is something locals do. The plan I would suggest are:
Take a cab and go to “Ask cafe” @kurucesme for a nice local style breakfast .
And then walk to Ortakoy which is an authentic part of the city, walk into the narrow streets near the sea where you will see a street bazaar. ( you can have a nice view of the bridge that connects europe to asia)
Go for lunch to arnavutkoy territory and have fresh fish in “adem baba” restaurant. Or at the same place there is a restaurant called “bodrum manti” where you can try amazing turkish style ravioli served with yougurt on top ( suggest the fried version).
Then walk to @bebek by the coast and have a afternoon cocktail in “bebek oteli rooftop” or “lucca” with nice crowd and music. Also you may have a local desert in “baylan patisserie” there if you are not up for alcohol.
For dinner I would suggest (http://balikciapo.com/m/ balikci abdullah) a must try fish restaurant you need to call them and they will pick you from a spot near the coast near bebek with a boat and take you to the restaurant so you will enjoy bosphorus by the sea with this occasion.
Monday ( old city tour)
One of the best traditional local breakfast place (https://g.co/kgs/A1hp1n ) Namli restaurant @karakoy. And after breakfast walk around the same building to the opposite side of the building and you will see a big baklava sweet store ( named: Gulluoglu ) which is great to taste beloved turkish dessert baklava in many choices.
Then take a walk on the galata bridge heading towards @eminonu which is the famous old city.
First attraction you will see when you cross the bridge is spice market ( misir carsisi) walk through out the other side of it from inside and you can head towards “yerebatan sarnici” , “ topkapi muzesi “ , “ ayasofia museum “ and then start climbing the hill behind it heading to blue mosque. When you finnish visiting blue mosque. A must try restaurant is “sultan ahmet koftecisi “ (Tarihi Sultanahmet Köftecisi Selim Usta
Alemdar, Divan Yolu Cd. No:12, 34110 Fatih/İstanbul, Turkey 0090 212 513 64 68
https://goo.gl/maps/nht4pBRF1TYRGX3EA make sure you take the right one as there are many copies). And the. Continue walking up the hill to the grand bazaar where you can have lots of interesting local stuff and i suggest trying turkish coffee there.
Also there is a traditional Hamam in Eminonu 🙂 if you want to experience “cemberlitas hamami” real experience.
And for dinner in eminonu there is a great kebap restaurant called hamdi for which best if you take a taxi as its down the hill. ( make sure you try katmer for desert )
Tuesday ( trendy friendly shopping tour )
Walk on istiklal caddesi first down heading direction towards karakoy and see Galata tower and surrounding atmosphere. Then walk up the istiklal caddesi heading the opposite direction and finnish the street and continue walking to @Nisantasi this is the one of the most trendy places in istanbul ( kind of soho in istanbul)
Walk in to nisantasi and narrow streets that are all located around a famous fashion retailer called Beymen store ( if find the store you will walk the streets around it as they are all nice) ( there is a museum called harbiye navy museum which is interesting focusing marsh soldiers sings if you plan timing ahead you can see a show too)
For lunch, time to meet with great Turkish Doner kebap in “tatbak restaurant “ order Iskender Doner (Tatbak Restaurant, in Teşvikiye, Akkavak Sk. 38/B, 34365 Nişantaşı/Şişli/Şişli/İstanbul, Turkey +90 212 246 13 06
https://goo.gl/maps/zEkBWPoSkrwomAfTA ) and you can then have a desert if you like in “Saray lokantasi” saray muhallebisi is a great desert.
And then you can walk down the hill to @besiktas “ dolma bahce sarayi” where ataturk lived and died.
Dinner “vogue restaurant “ trendy and hype nearby or “ alaf2tek” bit far and pure turkish meze experience.
Other ad hoc recommendations:
Kiyi restaurant great fish restaurant
Balikci kahraman best turbot fish restaurant in the world
Istinye park shopping mall, amazing mall for shopping
Bomonti bira fabrikasi nice events venue
Nusret best steak house
Kiz kulesi an island in the mid of the bosphorus to see.
Bosphorus boat tours you can take from ortakoy.
Kokorec very local turkish night food
Mangerie very trendy breakfast place in bebek with nice view.
70lik meyhane boutique turkish meyhane for raki and meze food
Karakoy for boutique stores
Galata24 on the rooftop of georges hotel for coctail and nice view.
Nuteras for a coctail in taksim with old city view
Karakoy mukellef and karakoy lokantasi are two great traditional turkish food restaurants both in Karakoy.
Lebi derya is also a restaurant with local food including proper steak as well as fish together with a nice view on the terrace.
Hope this article gives you a good idea about things to do in Istanbul.