A threatened Victorian swimming baths has been given Grade II* listed status.
The Health Hydro in Milton Road, Swindon, has been upgraded from Grade II listed status by Historic England.
Operator Greenwich Leisure Limited had said it was considering converting it into residential space but a petition urging the firm not to close or alter the baths attracted 7,000 signatures.
The upgraded status would mean Historic England would have to be consulted about any renovations or developments.
Historic England said it upgraded the status of the building, which is owned by the local authority, in recognition of its historic and architectural interest.
The hydro was designed to provide health and welfare services for workers at Brunel's Great Western Railway repair works in the town in the early 1900s.
As well as swimming and Turkish baths, the building housed numerous medical services including a dispensary.
Sally Hawson from Save Swindon's Heritage, the group that set up the petition, said: "I am delighted that this building has finally got the listing it deserves and the recognition that it is a unique gem that merits protection for future generations.
"I am hopeful that this new grading will now provide the protection this building has been crying out for and that greater respect for the building will now be enforced by the council."
In June, Historic England and the local authority announced they would jointly invest £7.6m in regeneration works which included improving the condition of the hydro.
Dale Heenan, from Swindon Borough Council, said: "The council welcomes the outside recognition that this building is now of national importance and is of special interest, warranting every effort to preserve it."
In 2016, Greenwich Leisure Limited announced it would conduct a feasibility study into "the best way to secure the future of the Hydro for generations to come".
At the time it said the building "has numerous long-term maintenance issues, resulting in the hydro currently operating at a loss".
The company has been approached by the BBC for comment.