The high popularity of ultra-wideband technology for accurate indoor positioning in industrial and public spaces has led to a large amount of research in recent years. The focus has mostly been on localization accuracy in small-scale setups with a single localization zone. However, solutions designed for line-of-sight environments are not suitable for many large-scale applications. To overcome this lack of research, we propose novel concepts for precise wireless multi-hop clock synchronization and localization zone selection. By integration into a time-difference-of-arrival-based ultra-wideband localization scheme, continuous cross-spatial positioning in large-scale scenarios is enabled. Validation is carried out in an unprecedented testbed with multiple rooms. We could show that positioning accuracy in multi-room scenarios is up to three times higher when exploiting the proposed concepts compared to the initial accuracy achieved with existing approaches. In addition, we provide an open-source implementation of our real-time localization system.