With the advent of advanced communication technologies, tech centers were largely replaced by communication centers, which combined the traits of radar stations and technology centers, or "wonders" like Temple of Nod. However, tech centers were still being built, as massive research facilities. They were essentially three geodesic domes interlinked by a massive concrete structure. The linking structure was usually used as storage space or parking lot and typically had two levels, connected by a freight elevator. The three geodesic domes could be arranged to fit whatever purpose the facility was to serve. GDI often used them as prisons, with domes filled with prison cells, while Nod usually employed them as regular research facilities. One of the main ReGenesis research centers was established by the Black Hand beneath a tech center, with the domes serving as Tiberium weapons and astronomy research centers, with one being a holding area for test subjects.