A growing number of initiatives in disparate scientific domains arose in the last decade, with the common goal of clustering data and services resources across Europe and make them integrated, open, sharable and available through infrastructures built according to FAIR principles[1]. In this context, the European Plate Observing System (EPOS[2]), now in its Implementation Phase and soon getting to the status of ERIC, is a long-term plan to facilitate integrated use of data, data products, software, services (DDSS) from distributed research infrastructures in Europe in the Solid Earth Domain. Its innovation potential consists in the opportunity of integrating distributed heterogenous resources from European, National and institutional resource providers, and making them available in one single environment. EPOS technical architecture has three main layers: a) National Layer of data providers, that provide access to DDSS; b) community-specific, European-Wide Thematic Core Services (TCS) layer, that collect and integrate DDSS from specific sub-domains and make them available at European level; c) EPOS Integrated Core Services (ICS) system where the integration of DDSS occurs. The architecture relies on three main concepts: Metadata: it is fundamental for describing assets and resources managed by ICS. A twofold approach was used for metadata: at metadata management level, the CERIF model was used for storing all information within the system; at metadata transfer level, an extension of DCAT-AP[3] was created (EPOS-DCAT-AP[4]) to facilitate TCS metadata collection. An architectural approach based on microservices that ensures scalability, flexibility and system interoperability. A harmonization process, that focused on technical aspects like data formats and protocols to access DDSS, but also required intra-domain work on semantic interoperability that includes adoption of common standards and vocabularies. We will discuss these topics and show a demonstration of the ICS prototype. [1] https://www.force11.org/group/fairgroup/fairprinciples [2] https://www.epos-ip.org/ [3] https://joinup.ec.europa.eu/solution/dcat-application-profile-data-portals-europe [4] https://github.com/epos-eu/EPOS-DCAT-AP/