GreenSign Institut, based in Berlin, is a leading provider of sustainability certifications for the hospitality industry in Germany. Since 2015, it has offered a transparent and practical assessment system, evaluating over 130 criteria across environmental, social, and economic dimensions. Recognized by the Global Sustainable Tourism Council (GSTC), GreenSign certifications—including Hotel, SPA, Gastro, Office, and Circular—align with international standards such as ISO 14001 and ISO 26000. The certification process involves a self-evaluation and an on-site audit, culminating in a three-year certification that supports continuous improvement.