Were these structures built by Aliens (Ancient Astronauts) or these are the remnants of a lost civilization of earth like Atlantis or Lemuria? There are vey different point of views regarding this subject. One side defends the alien intervention both in evolution of human itself and its technology, the other side specifies that all these tsructures have been buşlt by human themselves which lived thousands years ago in Atlantis or Lemuria and destroyed with a natural disaster like polar shift.
The earth until now has come across with many changes. The continental movements change the geographical shape of the planet. Once Europe as complete continent was under oceans, with the help of the dynamics of the earth it became a solid land. India's main location was exactly near today's Madagaskar. In million years it came towards Asia and the combination of the two continents formed the Himalayas.
The north pole as well always changed its location due to regular polar shifts. During ice age the glaciers could be seen in north America and Alpes in Europe. Our planet is very dynamic and during these changes it may harm the civilizations on it.