Covão dos Conchos

High in the Serra da Estrela, at around 1,500 metres, a small mountain lake drains into what looks like a hole in the surface of the water. Covão dos Conchos is an artificial lake, and its centrepiece is a perfectly round bell-mouth spillway: a stone funnel rising from the lake into which the water pours from every side at once, vanishing into the ground as if down a giant plughole. Around it lies the bare, boulder-strewn granite plateau typical of Portugal's highest mountain range.

The funnel is a piece of mid-twentieth-century hydraulic engineering rather than a curiosity built for show. It was constructed in 1955 to divert water from the Ribeira das Naves stream to the Lagoa Comprida reservoir, and it forms part of the hydroelectric system of the Serra da Estrela. The spillway is 4.6 metres high and 48 metres around, and the tunnel that carries the water away underground is 1,519 metres long. Over the six decades since its construction, moss and low vegetation have colonised the rim of the funnel, softening the concrete into something that looks almost natural.

For most of its existence the spillway was known mainly to engineers, shepherds and hikers. That changed in 2016, when photographs of the funnel spread widely online and turned this remote corner of the Serra da Estrela Natural Park, in the territory of the mountain village of Sabugueiro, into one of the most recognisable images of the range. It is reached on foot: a trail of roughly 9 km there and back leads across the plateau from Lagoa Comprida, the largest reservoir in the mountains.

Getting there

Covão dos Conchos lies in the Serra da Estrela about 13 km from Covilhã in a straight line, and about 7 km from the village of Sabugueiro. The nearest airfield is Viseu (VSE), about 47 km away; the main international airports serving the region are Porto (OPO) and Lisbon (LIS). The lake is reached by a walking trail from the Lagoa Comprida reservoir.