The Barcelona Convention, and its instrument the Protocol for Integrated Coastal Zone Management (ICZM), entered into force in 2011 with the goal of defining a set of common principles to achieve sustainable development of the coast along Mediterranean countries. Among other challenges derived from the implementation in the Member States is the need of a framework based on a governance platform to support countries in this process. In this context in 2010 the European Commission Framework Programme 7 for research funded a significant project called PEGASO, whose main goal was to construct such ICZM Governance Platform as a bridge between scientist and end-user communities. One of key elements of the Platform was the development of a Spatial Data Infrastructure (SDI) and a set of sustainability assessment tools required for making multi-scale integrated assessments in the coastal zone. The SDI was based in a network of local geonodes in order to deliver a Mediterranean and Black Sea harmonised sets of data accessible through a dedicated webbased Geoportal. This paper describes the development of the infrastructure, the process of integrating data from diverse formats and nature, and the challenged faced when trying to put in practice a common model to manage complex regions such as the Mediterranean and the Black Sea.