It’s one of the most unique natural parks that’s still alive in Istanbul, it’s about 40Kms from the center of the Asian side of Istanbul (Kadikoy). It is easy reachable as you can get to it by two minibuses.
From Harim you can go to Gebze by Minibus and from Gebze you can take another minibus to Tavşanlı where you will go out there and walk about one hour through the nature to reach to this canyon.
The canyon is approximately 14 KMs long and it ends in another village which also have public transportation means (Hourly) but it may vary on the weekend.
Location:
https://goo.gl/maps/jT2Apu9aXPS2
Location:
https://goo.gl/maps/jT2Apu9aXPS2