The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is dedicated to banning nuclear explosions worldwide. It was negotiated and adopted by the Conference on Disarmament in Geneva to comprehensively prohibit nuclear testing underground, underwater, and in the atmosphere. It was opened for signature in 1996 and will enter into force as soon as all 44 nuclear technology holder countries, as denoted in Annex 2 to the Treaty, will have signed and ratified it. Germany signed the CTBT in 1996 and ratified it in 1998, thereby committing to establish a National Data Center (NDC) and to install, operate, and maintain five stations of the International Monitoring System (IMS) for monitoring the compliances with the Treaty. Contributions on various CTBT related topics by authors from the Federal Institute for Geosciences and Natural Resources in Hannover (Bundesanstalt für Geowissenschaften und Rohstoffe, BGR), which has been mandated by Germany as the NDC, are presented in this book. Studies on institutional, technical and scientific aspects in the CTBT context are described to highlight recent, current and future work at the German NDC and to contribute to the CTBT monitoring and verification tasks. Nevertheless, this book focuses primarily on those aspects of the verification regime where BGR has expertise as well as BGR's activities and responsibilities as the German NDC and an IMS station operator during the last twenty years. An overview of the CTBT history, verification, and implementation in Germany is provided together with a description of the five German IMS stations and the seismology, infrasound, hydroacoustic and radionuclide technologies. Studies on the global performance of the IMS technologies to detect, locate, and identify nuclear and non-nuclear events are presented, as well as various case studies on the application, testing and benchmarking of these technologies. These case studies include, in particular, the North Korean nuclear weapon tests from 2006 to 2016, but also the National Data Center preparedness exercises from 2007 to 2013, the Tohoku earthquake with tsunami and Fukushima reactor accident in 2011, and the Chelyabinsk meteoroid explosion in 2013. Further studies are related to considerations on the quality of CTBT International Data Center waveform products, and to the usefulness and potential of satellite remote sensing in CTBT context as a National Technical Means (NTM). Finally, the role of On-Site Inspection (OSI) in general and, specifically, Seismic Aftershock Monitoring Systems (SAMS) are discussed for investigating potential treaty violations as the ultimate step in the verification chain.