Covão dos Conchos, Artificial lake in Serra da Estrela Natural Park, Portugal

Covão dos Conchos is an artificial lake in Serra da Estrela built with a distinctive spillway of granite and concrete featuring a circular opening roughly 48 meters around and 4.6 meters tall. A tunnel system connects the lake to hydroelectric facilities downstream, allowing water to be directed for power generation.

The bell-mouth spillway was built in 1955 to divert water from Ribeira das Naves to Lagoa Comprida, as part of the Serra da Estrela hydroelectric system. The funnel stands 4.6 metres high with a circumference of 48 metres, and the tunnel that collects the water runs 1,519 metres. Photographs of the hole went viral in 2016, bringing the lake to wider attention.

The lake lies in the territory of Sabugueiro, a mountain village whose residents have long used these high pastures. The spillway became known worldwide only in 2016, when photographs of the hole spread through social media. Moss and other vegetation have grown on the funnel's mouth over the last 60 years, and the vegetation now forms part of what visitors come to see.

The lake lies in the Serra da Estrela mountains near the village of Sabugueiro, within the Serra da Estrela Natural Park. The spillway is reached on foot; the surrounding terrain is high mountain, so check weather and trail conditions before setting out. The funnel rim is often edged with snow or wet ground, and the opening drops vertically, so keep a safe distance from the edge.

The funnel is 4.6 metres tall with a circumference of 48 metres, and the tunnel that carries its water runs 1,519 metres. Moss and foliage have grown over the mouth of the funnel in the decades since 1955, so the rim reads as a grassy ring rather than bare concrete. Photographs of the hole went viral in 2016, which is how most people learned of it.