Supergravity Walls as Windows into New Types of Vacua

Within four dimensional (4d) N=1 supergravity theories we present extreme dilatonic domain wall solutions with a general overall coupling $\alpha$ in the dilaton K\" ahler potential. We concentrate on extreme Type I walls, which are static, planar configurations, interpolating between Minkowski space-time and a new type of space-time with a varying dilaton field. $\alpha=0$ case yields extreme ``ordinary'' supergravity walls between Minkowski and anti-de Sitter space-times. For $\alpha=1$ the walls are extreme ``stringy dilatonic'' walls of the three level superstring vacua interpolating between the constant and linear dilaton vacuum. Extreme stringy dilatonic walls ($\alpha =1$) serve as a dividing line between the walls ($0<\alpha<1$) with the (planar) singularity covered by the horizon and those ($\alpha>1$) with the naked singularity. Striking similarities between the global space-time structure of such domain walls and and the one of the corresponding extreme charged black holes with a general dilaton coupling are pointed out.