automobilized city. Later World's Fairs continued to utilize immersive image techniques, as at Expo 2000 in Hanover, where the principle of immersion played a central role in the theme park «Mobility.»

From this brief sketch of the historical development of immersion, it is apparent that over time, older image media lose their use value; however, their importance as spaces for artistic experimentation increases. Increases in suggestive power and visual impressiveness were often the goal and driving motivation behind the development of new media of illusion. On closer scrutiny, we can make out a sheer endless stream of supposedly established entities, like cinema, that are revealed as assemblages of components that are arranged in ever-changing and new constellations in the kaleidoscope of developing evolution of art media. An overview provides some idea of the momentous energy involved in the constant search for and creation of novel spaces of illusion.

Immersion as a concept

As a rule, virtual realities that are primarily experienced visually seal off the observer hermetically

from external visual impressions, appeal directly through the use of threedimensional objects, expand the perspective of real space into illusion space, observe scale and color correspondence, and, like the panorama, use indirect light effects to make the image appear as the source of the real. In the case of virtual realities, the creator's intention is an artificial world that renders the image space a totality or at least fills the observer's entire field of vision. Unlike, for example, a cycle of paintings representing a temporal sequence of successive images, these images integrate the observer in a 360° space of illusion, or immersion, where there is unity of time and place. Image media can also be described in terms of how they intervene in perception, how they organize perception and cognition; in this respect virtual immersive spaces must be classed as extreme variants of image media, which, because they represent a totality, offer an alternative reality. On the one hand, they meet the demands of the media-makers for a symbolic form of an all-embracing image experience, which admits no contradictions or alternatives, and on the other hand, they offer the observers—again because of their