A pop up hostel for a hospitable Milan Laura Galluzzo, Vanessa Monna Mobility has become a foundational trait of the contemporary man, and in particular it is closely linked to the temporary nature of living today. It shows the changes of the post-industrial society. In fact, while the mobility of the modern society was called push-pull as migrations took place according to the attractiveness of the areas based on the criteria of job opportunities, in contemporary society’s more complex structure, mobility transforms and responds to different and more varied needs 1 . Modern cities are crossed by continuous streams of information, data, and people. The city of today is no longer occupied, as the traditional city was, by those living in it. The twentieth century has led to a radical change whereby the daytime population does not coincide with the population at night. Today, not only residents live in cities, so do new populations: commuters, city users and businesspeople. In particular, city users are tourists, street vendors, non-resident students, visitors, etc. 2 , each with different needs and different perceptions of the spaces of the city, each seeking the satisfaction of their needs 3 . The relationship between inhabitants and urban land has changed dramatically. Temporary design has become an excellent instrument to occupy peripheral, degraded, and under-utilized areas of a city and give them a new personality and new value to then find a more permanent form of use for them. In this sense, the temporary city is one that takes the least used areas and aspects and transforms them in order to accommodate new uses, new identities and new inhabitants. It can be said that today the meaning of the term “living” is always larger and indicates more activity than the meaning strictly related to an overnight stay and, therefore, to the small domestic space, a phenomenon shown by the fact that today we live at work, we live on the go, we live in the movement. As a result of all the transformations that have taken place in urban areas in recent decades, as we have previously summarized, the practice of urban tourism has strengthened: cities are becoming more and more centres of attraction for tourism and this should make us reflect on the response that our cities are capable of giving to the growing demand in this sector. In particular, the aspect of social and environmental sustainability in the management of these flows of tourism is becoming increasingly valuable, so it is essential to talk about a city using the metaphor of a sponge, an image that represents a system that is able to change shape and adapt to the needs of and the demand for hospitality. One can cite a number of examples of temporary hospitality, such as camping or temporary urban hotels, pop-up hotels, disseminated hotels, portals of domestic hospitality and the growingly diverse forms of urban hospitality that allow the city to "open" and "close" for events. A hospitable city is one that manages to build a strong relationship between its citizens and non- resident inhabitants, building positive outcomes for all the different populations within it at any given time. And what about the city of Milan? The city is not a typical tourist destination but it is well integrated in other tourist circuits. In the first place, the tourism in Milan remains a business, work related, and then you will find medical tourism formed by the growing number of patients who come to Milan from other areas. An interesting aspect typical of the Milanese hospitality industry (and in general of urban hospitality) is what happens at the events that the city hosts periodically such as Design Week, Fashion Week, the Milano Film Festival and many others. These are the weeks when the city hosts a huge number of visitors and insiders, often even without having suitable facilities to house them. In particular, on the occasion of the Salone del Mobile in Milan, the demand for hospitality on the part of designers and users is so vast that the facilities at a distance of miles away are fully 1 Montanari 2008: 40 2 Martinotti 1993, Nuvolati 2007 3 Fassi 2012: 35