Emulated networks and systems, where router and server software are run in virtual environments, allow network operators and researchers to perform experiments at large scale more economically than in testbeds. Running real code provides a greater level of realism than simulation.However, large scale comes with a problem: running real software means each test needs at least as much configuration as a real network. To recognise the true value of emulation at scale, we need to reduce the complexity of building, configuring, deploying, and measuring emulated networks. We present a system to facilitate emulation by providing translation from a high-level network design into a concrete set of configurations that are automatically deployed into one of several emulation platforms. Our system can be used to construct multi-domain networks in minutes, and is scalable to networks with over a thousand devices. It is modular, allowing support for different protocols, topology designs, and target platforms: Quagga, JunOS, IOS, etc. Users, from both the research community and industry, have already demonstrated its value in research and education.