Been testing this route for three weeks while staying in Sultanahmet. Start at Gulhane Park main entrance (near Topkapi) and follow the coastal path all the way to Sarayburnu Point where Golden Horn meets the Bosphorus. Completely flat, well-maintained surface, unbeatable water views for the full 2.5km each way.

Best window is 6:30-8am before the tour groups descend and before it gets too hot. You'll pass sections of the old Byzantine sea walls and get completely unobstructed views across the water. Surface is perfect for interval work if that's your thing.

Water fountains available in Gulhane Park for hydration stops. You might encounter some tour groups near the Topkapi entrance but the waterfront section stays clear. Safe for solo runners from dawn to dusk.