The proposed chapter deals with the fourth sector (4S) infrastructure based on the case study of the city of Havířov (the Czech Republic), its central heating company (HTS-Havířovská teplárenská) as well as with its non-profit endowment fund "Heat on the palm" (TND-Nadační fond Teplo na dlani), their activities and style of operation. The chapter touches on the scientific branches of the 4S, Corporate Social Responsibility (CSR) and strategic management. The main goal and purpose of the chapter is to characterise the 4S ecosystem and its dynamic equilibrium with the city of Havířov which represents that kind of municipality-based activities in the Czech Republic. The case study is methodologically supported by a theoretical introduction into basic concepts and definitions, review of relevant scientific literature, analytical and synthetic approach to the open and reserved information sources, interviews with representatives incorporated into the factual content of the text, SWOT analysis, strategic proposals and graphical outputs form the methodology of the chapter. The descriptive case study results of the 4S ecosystem are structured as follows: basic characteristics and historical background of the city Havířov, localisation, twin cities' population, social sphere, municipal and non-profit organisations and enterprises, sustainable enterprising, labour market, schools, national minorities, safety, crime and drug prevention, sport, cultural events, volunteering and awarding, associations, cooperatives, churches, smart city, digitization, infrastructure, bike sharing, gender policy, COVID-19 measures and SWOT analysis. The 4S and CSR activities of HTS and TND are characterised as well. The main results show a well-established and robust ecosystem of the 4S of the city of Havířov based on its municipal and private sector cooperation struggling to track the sustainable goals in all spheres of citizen life. Being aware of the dynamic development, further strategic goals highlighting economy, workforce, security, management, education, culture and leisure, health care and social sphere, transport and infrastructure are suggested by the municipal strategic plan. In conclusion, the authors suggest further improvements regarding small water cycle, public-private partnership (PPP) and community self-sustainability projects.