The concept suggests a reinterpretation of the riad typology, a block relatively closed on the outside, directed on itself and opened on a private space (a central courtyard, around which the block is organized, often with trees and a fountain). The facade of the riad is similar to an outside crust, kind of a closed raw bark, in opposition to the internal space, an opened core with a much finer treatment. The public space develops around this crust.