Mogao Grottoes are the crystallization of the wisdom and wisdom of ancient peoples. The location of Mogao Grottoes in the oasis of the Gobi Desert reflects the idea of isolation between Buddhism and the world, and integration with nature. The surrounding green trees form a unique quiet scenery. The honeycomb-shaped caves of Mogao Grottoes do not exceed 40 meters at the highest point. In winter, the sand blown from the west passes by the top of the cave, and the cave cannot be blown: in summer, opposite The Sanwei Mountain in the mountain has become a natural barrier, so that the sand blown from the east cannot threaten the cave. In this way, the Mogao Grottoes have become the safest area in the dry area. For this reason, although the Mogao Grottoes have passed the millennium, The 492 caves of 11 dynasties and a large number of murals and sculptures have been preserved intact, leaving a precious cultural and artistic heritage for the world. What does this text mainly explain? ['The Thought of Harmony between Man and Nature in the Design and Construction of Mogao Grottoes.', 'The important value of Mogao Grottoes in the history of world culture.', 'Why the Mogao Grottoes and their frescoes are well preserved.', 'The natural environment and unique tranquil scenery of Mogao Grottoes.']