This natural dwelling is described as a safe haven from enemies and other predators, composed of natural walls that lacked something to make this protective structure complete.
Doors not only offered protection but also sealed off the heat of buildings or houses.
The first recorded history of doors is found in Egyptian tomb paintings 4000 years ago.
Some of the heaviest doors in modern history are found in bank vaults, protecting huge sums of money and even millions in precious jewelry.
Despite this, the world’s heaviest door is not found in a bank, but actually in a laboratory.
A 44-ton (97,000 lb) door fragment, 2.5 meters thick and 3.6 meters wide, is located at Lawrence Livermore National Laboratory.
You’d think it would take a huge man to open such a heavy door, but thanks to the ingenious technology hidden in the door’s hinges, it only takes one person to open.
Lawrence Livermore National Laboratory – aerial view.
So what’s behind the door?
What is so valuable that such a huge structure is needed to protect it?
Funnily enough, the door is not designed to protect the contents inside the lab, but to protect the world from what’s inside the lab.
Lawrence Livermore National Laboratory has been used for many years to test various metals and other substances at the level of neurons.
The door is used to protect the Rotating Target Neutron Source-II (RTNS-II), the world’s most intense continuous fusion neutron source.
Scientists around the world have used it to study the properties of metals and other materials that could be used deep inside the fusion power plants planned for the next century.
The power of this technology involves a lot of radiation, which is why such a large and thick door is needed to prevent radiation from escaping the lab into the world.
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