A remote lake in Portugal has a "cave" landscape. What's going on here?

This "cave" in Portugal is actually just a modern water conservancy project, and there is nothing particularly mysterious.

In 2006, three young people came to the Esch trela Mountain Reserve in Portugal for outdoor activities. When shooting with drones, they found an amazing scene, that is, on a nearby lake, a huge hole appeared, and the lake kept pouring down, which looked like a "hole" on the water surface, shocking.

In fact, these three young people are all professional photographers. They heard that there was such a scene here, and they brought a drone to look for it. Because the terrain here is sinister and uninhabited, three professional photographers searched for a long time before finding this place. They made a lot of videos. Once the video was released online, it immediately attracted the attention of a large number of netizens.

In fact, this is a water conservancy project built by 1955. This is a shaft spillway made of concrete and granite. In the shaft dug in the rock, it drains downstream through the exit tunnel. It consists of bell mouth, shaft and exit tunnel. This so-called "underground hole" is actually the bell mouth of the spillway.

There is also a large water outlet tunnel under this bell mouth, which leads to the downstream river. This kind of shaft spillway is widely used all over the world, which is not uncommon. This is the water conservancy project in Portugal. At that time, it happened that the lake rose sharply, and the lake was rapidly flowing to the bell mouth, forming a spectacular scene that attracted many people's attention.

There are holes in the earth. This is a huge blue hole, located in Belize City and Honduras in South America. It is a famous diving resort and has been listed as a world historical heritage by UNESCO.

The depth here reaches 123 meters. Seen from a distance, it appears suffocating blue. In fact, this is not a real hole, but a rare geological phenomenon.