Underground, partially anderground, buildings at a slope of a hill, iside the vertical front of a cliff, and over the ground where dirt, soil and vegetation are placed around them, but also combonations of all above. Their distinguish and connection among them is the common attitude and behavior. The common attributes refering to architecture and energy savings, internal space and function, enviroment and the structure itself. Finally their common practice, penetration in the ground.
  From a history inquiry to a consideration of structural character of these underground spaces, aim of the research is the comprehension and exmination of these motives which lead the creation and use of spaces with main attitude the penetration in the ground.
  In history these practices were mainly combined with the need to hide from enemies and environment, reflecting the need to survive. They were evolved affected by the specifitities of each location, as the morphology and the climate, combined with the requirements of each user.
  Today these structures appear as free architectural choice, in times where more than ever people must confrort problems as unlimited energy consumption and increased density of buildings. Effects which underground spaces can encounter successfully. As a result, their desing is mightily supported, as units or parts of urban planning.
  By looking in the ground and following the path of penetrating architecture, the viable space is redifined and new prospects are opened up, with propitious circumstances about the environment