These are the three holes in our planet two natural and the other man made.
Croatia has 2 of the worlds deepest natural holes, and is home to the deepest vertical drop on the planet that has been discovered. The deepest drop on the planet was discovered by a cave explorer, this cave was discovered in a mountain range in central Croatia. It has a weaving drop of 62 meters which leads to the worlds biggest discovered vertical drop measuring at 516 meters deep. The cave can be found in the Velebit regions in Croatia, and the name of the cave is the Velebit Cave.
The Marinia Trench
Situated in the North Pacific Ocean surrounded by Japan, China and the Philippines and Papa New Guinea, lays the deepest point on our planet. It reaches the planets crust 6.78 miles below sea level. The trench is the boundary lines between two tectonic plates and they often hit off each other causing earthquakes and large waves that smash the shore lines. The pressure down there under the water is a thousand times more dense than our atmosphere itself. There are still species of fish and other creatures that have gone undiscovered because we as humans don’t have the means of getting down there as of yet to explore the depths safely.
Kola Well In Russia
The Kola Well in Russia is the deepest man made hole in the world measuring at 8 miles in depth, it is also known as the hole to hell. They started this hole on the surface back in late May 1970, the reason for drilling this hole was to get scientific proof of what the planet was made from. They bored through rock that was over 2.7 billion years old, this gave the scientists all the information they could possibly need. As the technology advanced they started to send things down it to discover what it was actually like down there deep in the Baltic Continental plate. They were surprised to find water down there with the heat of the core of the planet, It was not like the water on the surface but it was water all the same, this water was made up from the gases and minerals that lay beneath the surface. This intelligence led to space exploration missions to discover if there was water on any other planets in our solar system. This is an on going exploration of our planets formation and our neighbouring planets.