The Plaça Reial of Barcelona has a high vitality, with pedestrian spaces and a variety of establishments in its vicinity.

Comparatively, Plaça dels Països Catalans has a low vitality, with fewer establishments and large, surrounding streets which inhibit pedestrian movement.

Urban vitality is the quality of spaces in cities that attract diverse groups of people for varied activities over frequent, varied times.^[1][2] These spaces may be perceived as alive, lively or vibrant, in contrast with low-vitality areas, which may repel people and be perceived as unsafe.^[3][4]

The urban vitality index is a measure of this quality and has become a fundamental tool in urban planning, especially in interventions for spaces with low vitality.^[5] The index is also used to assist the management of spaces that already have high vitality. However, the success of high-vitality spaces can sometimes lead to gentrification and overtourism that may reduce their vitality and initial popularity.^[6]

The concept of urban vitality is based on the works of Jane Jacobs, especially her most influential work, The Death and Life of Great American Cities. In the 1960s, Jacobs criticized the modern and rationalist architecture of Robert Moses and Le Corbusier, whose work centered private cars. She argued that these forms of urban planning overlooked and oversimplified the complexity of human life in diverse communities. She opposed large-scale urban renewal programs that affected neighborhoods and that built freeways through inner cities. She instead advocated compact and mixed-use development with walkable streets and “eyes on the street” to deter crime.^[7]

The concept of urban vitality is important in Mediterranean urbanism and its history, in which public space, walkability and squares are valued as centers of social interaction and cohesion, in contrast to the Anglo-Saxon urbanism of large, car-centric infrastructures with greater distances between conveniences.^[3][4][8]

Urban vitality can be quantified thanks to the analysis of the elements that determine it. Among them are:^[9][10]

• Diversity of uses of the space that can attract different types of people for diverse activities and at various times, making the space constantly occupied, improving its security.
• Opportunities for personal contact with blocks, buildings and open spaces that are not too large, as they reduce the number of possible intersections and social interactions.
• Diversity of buildings with varied characteristics and ages, allowing people with different purchasing power to live in all areas of the city, avoiding the formation of ghettos.
• High population density, residential areas are essential to attract other types of activity.
• Accessibility for all people without depending on private transport, with pedestrian access being the most important, as it is the most democratic, sustainable and cheap, followed by access by bicycle and public transport.
• Distance to border elements, such as large buildings, ring roads, surface train tracks or large urban parks that discourage the use of the street.