The aim of the OFELIA project is to create a unique experimental facility that allows researchers to not only experiment 'on' a test network but to control the network itself precisely and dynamically. To achieve this, the OFELIA facility is based on OpenFlow, a currently emerging networking technology that allows to virtualize and control the network environment through secure and standardized interfaces. In a nutshell, OpenFlow enables experimenters to change the behavior of the network as part of the experiment rather than, if at all, as part of the experiment setup. OFELIA will provide high-performance OpenFlow equipment to enable experiments at scale and to ensure that the facility is based on mature technology.Another strength of OFELIA is its concept of federated or interconnected islands. A set of five islands creates a diverse OpenFlow infrastructure that allows experimentation on multi-layer and multi-technology networks provided by the different islands. The facility will extend all the way from standard Ethernet to optical and wireless transmission and it will also include an emulation wall for scalability tests comprising thousands of nodes.The facility will grow in three phases to, on the one hand provide an early access to the facility (after 6 months already) and, on the other hand to evolve during the project lifetime, incorporating the feedback of the user community and extending its reach to other test facilities. Two open calls will be published to invite experimenters that bring their use cases and scenarios to the facility creating a feedback loop to extend the OFELIA facility according to the needs of the user community.