Re-discovering urban slabs. Towards a new understanding of multi-level public facilities.

This thesis discusses Urban Slabs, understood as built grounds that generate an ensemble of accessible new public places for recreation in the city. Research identifies two parts in an Urban Slab: 1) an above-slab well-delimited public space; and 2) an ensemble of below-slab spaces that are turned into public interiors. The above-slab space is a direct descendant of the long lineage of well-delimited central public voids representing the political and gathering spaces of the city, the Heart of the city, like public and market squares. The below-slab spaces, originally created for functional needs like the construction of storage spaces, the evacuation of used waters or the insertion of other flows and technologies deriving from the urban densification and congestion, have become new public spaces from the last hundred and fifty years onwards. The research hypothesis is that these multilevel and three-dimensional public facilities constitute contemporary opportunities acting as spaces for meeting and reassembling the collectivity in the city. Through case studies, research highlights different categories related to the above-slab space first and to below-slab spaces after. The goal is to inspire not only the conception but as well the reinvention of public grounds in the city and the transformation and re-use of existing urban vacancies. In this way, the notion of Urban Slab emerges as a convenient tool for contemporary and future reinventions of public spaces, where the collectivity can gather in a nonproductive context around recreational activities. Urban Slabs appear then as functional and symbolic hearts, centrally located in the city in which the urban collectivity can exercise its right to recreation, making use of public spaces for walking, playing, doing some sports, performing, or just gather as political acts. The topics of recreation and diversion, to which these Urban Slabs are functionally dedicated, become relevant in this research.