A significant amount of fifth-generation (5G) experimentation facilities and testbeds have been proposed in the scientific literature over the past five years, each characterized by its unique setup of resources and control frameworks. Given the wide set of often contradicting requirements presented by the various classes of 5G use cases, the 5G-EPICENTRE project focuses on the provision of a truly open, multi-site 5G experimentation facility specifically tailored to the needs of public safety solution providers, which will leverage on, and extend the capabilities of 5G testbeds developed in, or resulting out of the 5G-PPP Projects (Phase 1-3). At its heart, 5G-EPICENTRE will encompass best practices derived from Cloud-Native implementations, providing a platform for automating and streamlining 5G experiment deployment inside flexible, easily reproducible environments packed in lightweight software containers. 5G-EPICENTRE will focus on the provision of an innovative, open and interoperable platform that aims to act as both a testbed, as well as a federation of existing 5G testbeds. Through an augmentation of experimentation facilities, 5G-EPICENTRE will define the necessary information models to interconnect testbeds partaking in the federation through simplified APIs, and will facilitate the orchestration of their resources to optimally service the needs and requirements of PPDR-centric applications. © 2021 IEEE.