Quick answer
A fair question with a two-part answer. The canyon is real and ancient; the lake filling it is a reservoir. Here is exactly what is natural, what is engineered, and why both are true.
The honest answer is: both. Green Canyon is a real, ancient river gorge — but the calm emerald water filling it is a reservoir, held back by the Oymapınar Dam.
Verified July 2026
The part that is natural
The canyon itself was carved over a very long time by the Manavgat River as it cut down through the limestone of the Western Taurus. That gorge, the steep walls, the mountain setting and the water source are all genuinely natural. The Manavgat is fed by giant karst (limestone) springs — one of them, the old Dumanlı spring, was proposed in the peer-reviewed Journal of Hydrology (1980) as possibly the largest karst spring in the world. So the raw ingredients here are as natural as it gets.
The part that is man-made
What is engineered is the water level. Before 1984 this was a flowing river at the bottom of a deep gorge. Then the Oymapınar Dam, a concrete arch dam about 185 metres high, was built between 1977 and 1984 to generate electricity, according to the official Akseki district governorate. When the reservoir filled, it drowned the old river and the springs, and the water rose up the natural canyon walls. The still, deep, emerald surface you cruise on today is the surface of that reservoir.
So which name is correct?
Officially, it is the Oymapınar Dam Lake (Oymapınar Baraj Gölü). "Green Canyon" — Yeşil Kanyon — is the tourism name that operators gave the flooded gorge. Neither is wrong. One describes the engineering; the other describes what you actually see, which is a green ribbon of water winding between natural mountain walls. We use "Green Canyon" because that is what everyone searches for, but we do not pretend the lake predates the dam.
Why the confusion happens
It looks impossibly natural. There are no visible pipes or concrete from most of the cruising area; you see forested slopes, cliffs and a fjord-like waterway. The dam wall is only one feature at one end. That is why many visitors leave assuming it is a wholly natural lake, and why some marketing quietly encourages that impression. We would rather tell you the truth: nature made the canyon, engineering made the lake, and the result is genuinely beautiful either way.
Does that make it less special?
Not at all. The gorge is real, the karst springs are real, the depth is real, and the surrounding Taurus is real. What the dam added was a mirror-calm, sheltered waterway that is safe and scenic to cruise — the reason a boat day here feels so different from the open sea. If anything, the layered story makes it more interesting than a plain lake.
For the buried natural wonder underneath, read the Dumanlı spring under Green Canyon. For the engineering side in full, see our Oymapınar Dam facts. And if you are weighing this against a sea trip, our comparison of Green Canyon versus a sea boat day lays out the difference honestly.
FAQ
Is Green Canyon a natural lake?
No. The canyon is natural, but the lake is the Oymapınar reservoir, created when the dam was built between 1977 and 1984. Before that this was a flowing river in a gorge, so the water body you see today is engineered, even though its setting is entirely natural.
Then why is it called a canyon?
Because the gorge is genuine. The Manavgat River carved this deep valley through Taurus limestone long before the dam existed. The reservoir simply raised the water up the natural canyon walls, so "Green Canyon" describes the real shape of the landscape you cruise through.
Is the water really green?
Yes, it reads as emerald to green in most light. Operators attribute this to depth and mineral-rich spring water, and the municipality describes the wider Manavgat system as turquoise-green and mineral-rich. We present the colour as observed, without inventing a scientific figure for this specific lake.
Does knowing it is a reservoir spoil the visit?
Most visitors say the opposite. The layered story — an ancient gorge, one of the world's great karst springs beneath, and a modern dam — adds depth to the trip. The scenery is real and the water is calm and sheltered, which is exactly what makes the cruise so relaxing.