Emirgan Park, located near İstinye in the Sarıyer District (European side), is a nice park for running. Combine with a short waterfront path in around the İstinye for a pleasant run. It’s a lush, green oasis with about 3 km of paths around flower displays and two small ponds. A loop of the perimeter is ~2 km. Pro Tips:  The park is known for its tulip displays. İstinye can be reached by ferry from Istanbul (Beşiktaş), about a 45 minute ride. 

To extend the run, head north on the main road (decent sidewalk) for 0.8 km to the İstinye marina. There’s a pleasant dedicated walking path around the port, ending at the ferry terminal.