The modern advances of digital technologies provide a wider access to information, enabling new ways of interacting with and understanding cultural heritage information, facilitating its presentation, access and reinterpretation. The paper presents a working example of connecting and mapping cultural heritage information and data from cultural heritage institutions and venues through the open technological platform of the CrossCult project. The process of semantically representing and enriching the available cultural heritage data is discussed, and the challenges of semantically expressing interrelations and groupings among physical items, venues, digital resources, and ideas are revealed. The paper also highlights the challenges in the creation of a knowledge base resource which aggregates a set of Knowledge Organization Systems (KOS): a carefully selected subset of the CIDOC Conceptual Reference Model, a set of application ontologies and an optimised classification scheme based on domain vocabularies.