🇵🇹Portugal, Covandos-Conchos
There is an artificial lake in the Serra da Estrela mountains, in the middle of which there is a gaping hole. It looks like a portal to another dimension, but in fact it is a funnel leading to a spillway tunnel.
Lake Lagoa Serra da Estrela was created in 1955 during the construction of a hydroelectric power station. Instead of building a pipeline to circulate water between Lagoa Serra da Estrela and another lake, Lagoa Comprida, the engineers working on the project decided to drill a tunnel into the mountain.
The Covandos-Conchos discharge is designed to supply water to nearby settlements. The absence of other structures nearby gives the impression that this is a natural part of the lake. There is even grass growing on the slopes of the concrete funnel. Few people knew about this place until 2016, when photos with him began to be actively distributed by users of social networks.
https://goo.gl/maps/AWGY2X8QpowvtySN8