There is a vital need to electronically preserve our cultural heritage as well as the digital outcomes of today's research, arts and humanities. Due to the rapid pace of changes in information technologies, digital data, documents and records are likely to become uninterpretable bit-streams within short periods of time. Digital Preservation deals with the long-term storage, access and maintenance of digital data objects. Preservation experts have proposed an almost overwhelming variety of preservation actions and tools that may help to mitigate this risk but at the same time have disclosed a lack of empirical evidence in the process of informed decision making. In this paper we present the Planets Testbed - a collaborative research environment for scientific experimentation in digital preservation, built in the context of the European Integrated Project Planets. The paper presents the core architectural concepts, components and underlying methodology.