# Implementation of the 3-30-300 Green City Concept: Warsaw Case Study
## 1 Introduction  
Nowadays, the topic of green cities is being increasingly discussed, and attempts are being made to answer the question of how green a city should be [1], emphasizing the positive impact on citizens and their quality of life. There is a widespread belief that such areas are important for urban heat management, providing shelter on hot days [2], as well as for reducing the negative impact of climate change on the functioning of cities and their inhabitants [3]. Green spaces are recognized as key natural resources in a city [4] and also offer safe play areas for children, which contributes to their proper development [5]. Research also shows the importance of the greenness of a city on its sustainability [6]. The subject literature indicates that the presence of greenery in residential areas significantly impacts the health of residents. [PERSON] et al. [7] examined the relationship between proximity to green spaces and the occurrence of illnesses among residents. They sought to verify whether previous studies suggesting a positive effect of green surroundings on self-assessed physical and mental health could be confirmed by objective medical data. The results showed that the strongest connection with green areas was observed in cases of anxiety and depression. Another significant finding was that children and individuals of lower socioeconomic status benefited the most from the presence of greenery in their surroundings. Similar findings were presented by [PERSON] et al. [8], who aimed not only to confirm the relationship between green spaces and health but also to understand the mechanisms that mediate these relationships. Their research underscores that green areas can significantly improve the quality of life for city dwellers, positively affecting both their physical and mental health. The authors suggest that urban policies and planning strategies shouldfocus on increasing the availability of green spaces, which would significantly enhance the standard of living for citizens. They also emphasize that understanding this need is crucial for creating healthy and sustainable urban environments. In addition, a study carried out by another group of researchers, analyzing the existing works [9], also found that green spaces have an additional significant effect on stress reduction, Improved mood, or increased feelings of happiness, which may have an Impact on their health. The issue of living without access to greenery became particularly evident during the COVID-19 pandemic. Many people realized that, being confined at home, they only saw the grayness of a concrete city outside their windows, which might have exacerbated mental health issues and fears related to the pandemic. To confirm these observations, an analysis was conducted on the impact of green spaces on reducing COVID-19-related fears, general anxiety, and depression [10]. The results showed that depending on the age group, green spaces brought different benefits. In older participants, they reduced depression, while in younger groups, they were associated with decreased concerns about the pandemic and Its consequences. It Is worth noting that other studies conducted have also shown that the impact of greenery on mental health has a not-significant effect on reducing these problems [11; 12; 13]. Despite the numerous advantages of green spaces and their positive impact on health, many cities still lack sufficient green areas, often deemed adequate, nonetheless. To raise awareness among decision-makers and the public, it is necessary to clarify the concept of a \"green city\", which is not clearly defined and, therefore, is interpreted differently. This ambiguity leads to low interest in the topic and a lack of clear guidelines for Implementation. [PERSON] and [PERSON] [14] present an example of such an approach, arguing that a green city is one where every home is within a defined maximum distance from the nearest green space.