Jane Dodds hopes the ongoing development of a “Global Centre of Rail Excellence” in Onllwyn will boost employment in her region.
The Mid and West Wales MS said at the Senedd that it is “quite an incredible place” - covering nearly 1,000 football pitches in size and built to test the speeds of a train.
She said: “It is absolutely of global significance, and it's one of its kind on the international stage.
“But for me, it's the value it brings to the local community in places like Ystradgynlais, which I represent.
“Ystradgynlais has struggled with job losses from the town, like the Tick Tock factory and Dewhirst, as well, yet the community is actually really resilient and healthy and vibrant.
“Lloyds Bank left the town in 2023, leaving no bank in the biggest town in Brecon and Radnorshire, despite Lloyds Bank making a mere £7.5 billion in profit that year.
“The Welsh Liberal Democrats recently secured a banking hub for the town, which will help.
“But I'd like to ask the Welsh Government what else it can do to ensure that there are really good links with the economic development of the GCRE and towns and communities around Ystradgylais?”
First Minister, Eluned Morgan, said jobs are desperately needed in that part of the world.
She said she remembers, when she was first elected, seeing hundreds of people coming out of the Tick Tock factory.
Ms Morgan said: “All of that has been diminished, so we do need something transformational.
“I think this could be the ticket to that transformation. It will be imperative that local communities get to benefit from that and get to work on and with the organisations that are there to develop it.”
The Global Centre of Rail Excellence is a train, railway infrastructure and technology testing facility.