Cybersecurity experiments that involve private data or malware samples require controlled environments and an appropriate facility to collect and characterise them, or understand their operations without compromising the security of these data and the hosting institution. Using such facilities allows the researchers to carry reproducible and long term research activities in a safe environment, without worrying about side effects or loss of data. In this paper, we detail the design of a cybersecurity facility to carry such experiments, including malware collection and analysis, network telescopes and honeypots, or hosting critical services. The facility, aka High Security Lab (HSL), is running since 2010, and is widely used by multiple research groups to carry sensitive data cybersecurity experiments. It includes an evolving infrastructure with tools and processes for building and running long-term and reproducible cyber security experiments. We report on our experience and lessons learned from the design, the setup and the evolution of this facility during 10 years while focusing on major cybersecurity experiments that have been conducted by researchers.