A green-blue infrastructure is essential for achieving the European Green Deal objectives and can be used to protect large cities and their metropolitan areas against urban sprawl. Green-blue infrastructure is an important research topic, because green-blue planning networks provide solutions for mitigating contemporary growing urban and climate challenges. Our study aims to create an innovative methodology for defining and analyzing the elements of green-blue infrastructure and their connectivity within Bucharest, Romania and its metropolitan area, to serve as a planning model. The methodology consists of merging European geodata sets with metropolitan and local data, using GIS tools, and analyzing the connectivity within the study area. All connections resulted from implementing the Linkage Mapper tool were operationalized, using high-resolution satellite images and correcting obtained connections, so that deviations from reality were minimized. The results consist of a conceptual model for planning the green-blue infrastructure within Bucharest and in its metropolitan area, embedding an analysis of its connectivity. The study contributes to implementing the concept of green infrastructure in urban and spatial planning, providing tools for planning the green-blue infrastructures of large cities and their metropolitan areas and, implicitly, reducing urban sprawl, improving air quality and mitigating environmental threats due to climate change.