2. Macka Park: Formerly in the grounds of Dolmabahce Palace. There are a few cafes and, in summer, a small funfair and concerts.
3. Parkorman: It's kind of a yuppy spot offering great nature, activities, restaurants, swimming pool, concerts & raves time to time, etc.
4. Gulhane Park: Once the outer grounds of Topkapi Palace, Gulhane Park is today the largest open area in the old city.
5. Yildiz Park: Yildiz was once the grounds of Ciragan Palace. It's still in the hearth of the city letting you have a quick escape from the rush.
6. Buyuk Camlica: Istanbul's highest natural spot offers wonderful views
7. Burgaz Island: Great for a day trip full of fresh air, no cars, a lot of walking around the trees & history.
8. Polonezkoy: It was established as a Polish enclave in the middle 19th century. Only few Poles remain today, but the village's history and rural charm live on. Polonezkoy is popular with day-trippers for its old wooden houses and relaxing country walks. Also, availability of pork attracts people, since it's not common in Turkey (forbidden under Muslim law).
9. Taksim Gezi Park: This is the famous public park where the public uprising of summer 2013 took place. Environmentalists started protesting the municipality for trying to cut the trees in the park to be able to build a remake of old barracks, which would also be a mall. Thousands joined the protestors and it became the largest uprising in Turkey's history.
10. Goztepe Ozgurluk Parki: This is a local park on the asian side and is good for going for a run, taking your dog for a walk.