Bydd y Ganolfan Rhagoriaeth Rheilffyrdd Fyd-eang, cyfleuster profi trenau, rheilffyrdd a thechnoleg, yn cael ei lleoli ar safle glo brig Nant Helen yn Onllwyn, sy'n cael ei weithredu ar hyn o bryd gan Celtic Energy.
The Global Centre of Rail Excellence, a train, rail infrastructure and technology testing facility, will be located on the site of Nant Helen opencast mine in Onllwyn, which is currently operated by Celtic Energy.