The fascinating Covao dos Conchos, high in the Serra da Estrela natural park in Portugal is called the ‘eye’ by locals. This incredible man-made lake hole is actually a bell mouth spillway and well worth the short hike to get up close to the mesmerising spectacle, set deep in the rugged Portuguese mountains.
What is Covao dos Conchos?
Covão dos Conchos is an artificial lake in the Serra da Estrela mountains in Portugal, in which a bell mouth spillway has been set. A bell mouth spillway is designed like an inverted bell, where water can enter around the entire perimeter. These uncontrolled spillways are also called morning glory, (after the flower) or glory hole spillways.
The spillway was built in 1955 to divert water from Ribeira das Naves to Lagoa Comprida and is part of the hydro-electric dam system of Serra da Estrela. The engineered structure has a height of 4.6m and a circumference of 48m. Inside Cãvao dos Conchos is a tunnel that collects the water as it rushes in, which is a whopping 1519m long, before taking it to Lagoa Comprida.
It’s really only since 2016 that the outside world has been interested in this other-worldly Portuguese water tunnel, when a couple of images posted to Instagram went viral and exposed the little-known secret to the world. Since them, visiting the Conchos dam and hole is high on any Portugal bucket list.
Why Should I Visit Cavao dos Conchos?
Not only is the hole itself breathtaking, it is situated in the stunning Serra da Estrela, the highest range in continental Portugal and home to the tallest mountain in Portugal at 1993m. It’s a wild and unspoiled place with amazing views across the craggy granite mountains and the Dao valley. The whole area that you will cover hiking to Cavao dos Conchos is a designated GeoPark, formed millions of years ago by glaciers, which have left fantastic irregular boulder fields, huge exposed slabs of rock and deep ravines to explore. And of course, the beautiful Lagoa Comprida heralds the start of the hike and is perfect for a dip afterwards on a hot day.
Down the mountain is the pretty and hospitable town of Seia, where you will find traditional and local produce including wine from the Dao valley, cheese and the famous Seia bread.
When to Visit Cavao dos Conchos
You can visit at any time of the year as long as the road up to Lagoa Comprida is open. The Serra da Estrela is one of Portugal’s top winter destinations and snow in winter is definitely a possibility. The lake looks stunning when it’s frosted with ice, but the trails may well be icy too, so good walking boots and thermals are a must at this time of year.
In August it will be busy, especially at the weekends, with Portuguese locals driving up to Lagoa Comprida for a day of sun-bathing and swimming on it’s shores. It will also be hot, so take water, sunscreen and a hat if you’re planning on visiting in the summer.
September and October are good months, the weather will still be warm but the crowds much less. March and April are the wettest months, but with high rainfall and snowmelt volume, you’ll see the full force of the spillway in operation as water rushes into its open jaws, to start its descent to the lake. May and June are just about perfect with good water levels and ideal hiking weather!
Whatever the time of year, if photography or drone footage is important or you want the views, try and avoid the days when low cloud envelops the mountains.
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Getting to the Start Point
The easiest way to get to the trailhead at Lagoa Comprida is by driving from Seia on the N339 or Covilha, on the other side of the Serra da Estrela, also on the N339. The N339 is a normal two-way tarmacked road which is regularly driven by tourist coaches.
There is plenty of level parking at Lagoa Comprida, which is free of charge. If you’re touring Portugal in a motorhome or campervan, this is a great spot to stay overnight, although there are no services.
There are a few small shops selling local handy-crafts and foods, as well as a small cafe.
Hiking to Cavao dos Conchos
(this is a relatively easy hike and would score a one for difficulty, if not for a few sections of the trail which are tricky underfoot due to the uneven rubble and rocks, and the final bit of narrow dam which needs to be crossed to get to the viewing point for the hole.)
The start point of the hike is at the Lagoa Comprida. As you arrive, you will see the enormous (and pretty impressive) dam wall in front of you, which you can walk along for the best view of the lake. Park and as you face the dam, head left past the few shops. You’ll pick up the trail easily, as there is only one!
It is also possible to follow the trail to Cavao dos Conchos on a mountain bike, although less experienced riders may have to dismount for some of the more rocky sections.
Within a few minutes, you’ll have left the car park behind and be immersed in nature, with the vast lake spread out to your right and incredible views to your left. You’ll soon pass a circular bowl type area on your left which was where stone for the dam was quarried in the fifties.
The trail you are now on takes you all the way to the Cavao dos Conchos. You will pass a house on your right which is barely visible but you will notice on your return journey, although it has been set so well in it’s surroundings you might miss it unless you really search for it! The drive way is chained off and a little further on the track is a right fork which takes you to the lake. Don’t take this, keep on the current path. You’re about half way there at this point.
All along this track are intriguing slabs of rock, huge balancing boulders and little streams and waterfalls. If you like to get off the beaten path, allow a full day for this hike, you won’t be able to resist stepping off the trail to explore!
The small lake in which Cavao dos Conchos is sited will appear on your left, follow the track down along the side of the lake to the small concrete dam. You won’t be able to see the spillway from here though – it’s sort of hidden! Cross the dam (there is a path behind the dam wall), looking out for the hundreds of frogs in the waters below, until you reach the rocky slabs on the other side.
Make your way over these to the final hurdle – a narrow dam wall without a path. There is vegetation and a 2m drop on your right, with a 1m drop into water on your left, so not a catastrophe if you fell off!
Once safely over, follow the small path through the undergrowth to another rocky slab which is a great vantage point for taking pictures or launching a drone. A bit further on from this is the best place to see the spillway, right at the edge of the lake.
Your first view will take your breath away – this feat of engineering is in perfect harmony with the surroundings, hosting grasses and other plants growing in the opening. In the constant flow of fresh water, the flora and fauna around the hole are abundant and lush, with dragonflies darting in and out of the greenery and small fish and water insects easily visible in the clear lake.
There are dozens of tracks and trails around the lake and in the surrounding areas – there are at least three trig points visible on the hike. You could easily spend a week with a small tent hiking in the area and the geological nature of the mountain range makes the landscape in this part of Portugal particularly fascinating.