While migration is intrinsically linked to the arrival to the city, the city is also shaped by migration. It is an in-between space, between "territory" and "home", the border and shelter. However, "urban" hospitality remains a concept that needs to be explored. As part of an FNS research project inquiring on the place of newcomers in precarious situations in Geneva and Brussels, our thesis focuses on the Brussels context. The state of research shows that hospitality could be seen as a "quality" of environments, situations, settings, atmospheres, spaces, or buildings, like institutions and, even more so, firstly, hospitality is a place. Indeed, as a primary shelter and "refuge" par excellence, architecture is intimately linked to the question of hospitality. Placed over the long term - that of the installation -, hospitality invites us to take an interest in living there. Furthermore, architecture as media and translation is a tool for materially evaluating the policies of (in)hospitality at work. Based on the route and the experiences of several newcomers and on an urban ethnography - built up of interviews with hospitality stakeholders from civil, associative and institutional fields, numerous visits to reception centres, action research, voluntary work, participation in Brussels socio-cultural events on the theme, and monitoring of social networks and journalistic medias -, our research studies the spatiality, urbanity and materiality of hospitality policies and the (in)hospitality of architectural and urban policies. The questions that the research answers are the following: what access to the city and to housing does Brussels configure depending on whether we are migrants in transit, asylum seekers or long-term undocumented migrants? What opportunities are we entitled to and what limitations or threats do we face? What specific forms of uninhabitability do we encounter? What home are we allowed to build depending on your country of origin, your reasons for leaving, your racialization, your gender or, even, your resources? The inhospitality of spaces dedicated to reception raises the question of their (in)habitability: what do these spaces and places offer to the newcomer and their unique journey; what opportunities and rights do they provide? What autonomy and sociability can they hope for? In Brussels, reception policies tend to be deployed without architecture, in particular by placing newcomers "out of place" - through homelessness - and asylum seekers "out of town" - through geographical relegation. Ordinary hospitality then takes place in a different way in the built structure of the big city which remains a privileged environment for newcomers and long-term undocumented migrants to settle in. In doing so, dynamics reduce or undermine this other form, such as urban policies normalizing the exclusion of those considered undesirable. In this sense, with reference to Lefebvre's "right to the city", we ask: what urban inscription for alternative or plural expressions of hospitality? But also, who threatens the ordinary and "non-ordinary" architecture of hospitality today?